Sleep - What about it?

There's a little about sleep in the Q&A towards the end of A Still Forest Pool by Ajahn Chah,

Q: What about sleep? How much should I sleep?

A: Don't ask me, I can't tell you. What's important, though, is that you watch and know yourself. If you try to go with too little sleep, the body will feel uncomfortable, and mindfulness will be difficult to sustain. Too much sleep, on the other hand, leads to a dull or restless mind. Find the natural balance for yourself. Carefully watch the mind and body, and keep track of sleep needs until you find the optimum. To wake up and then roll over for a snooze is defilement. Establish mindfulness as soon as your eyes open.

As for sleepiness, there are many ways to overcome it. If you are sitting in the dark, move to a lighted place. Open your eyes. Get up and wash or slap your face, or take a bath. If you are sleepy, change postures. Walk a lot. Walk backwards. The fear of running into things will keep you awake. If this fails, stand still, clear the mind, and imagine it's broad daylight. Or sit on the edge of a high cliff or deep well. You won't dare sleep! If nothing works, then just go to sleep. Lie down carefully, and try to be aware until the moment you fall asleep. Then as soon as you awaken, get right up.

I read earlier that monasteries have a 6-hour-per-night sleep time scheduled (which is slightly less than the current lay tradition of "8 hours").

Why do Buddhist monks sleep so little?

Received wisdom in the West is that eight hours is optimal. But monks in Korea choose to get about six hours a night, day in, day out. Why?

Some people answering that question say it's possible because monks go to deep sleep quickly (so they use those 6 hours thoroughly), and the meditation they do during the day is comparatively restful.

As to Buddhist point of view what is sleep and how to cope with it?

According to Tenzin Wangyal Rinpoche's The Tibetan Yogas of Dream and Sleep,

All of our experience, including dream, arises from ignorance.

Then, he goes further:

This sequence of experiences shows us something about karmic traces. When the man was young, he reacted to the fighting in his home with fear, anger, and hurt. He felt aversion toward the fighting, a normal response, and this aversion left a trace in his mind. Decades later he passes a house and hears fighting; this is the secondary condition that stimulates the old karmic trace, which manifests in a dream that night.

In the dream, the man reacts to the dream-partner's provocation with feelings of anger and hurt. This response is governed by the karmic traces that were collected in his mental consciousness as a child and that have probably been reinforced many times since. When the dream-partner who is wholly a projection of the man's mind provokes him, his reaction is aversion, just as when he was a child. The aversion that he feels in the dream is the new action that creates a new seed. When he wakes he is stuck in the negative emotions that are the fruit of prior karmas; he feels estranged and withdrawn from his partner. To complicate matters further, the partner reacts from her karmically determined habitual tendencies, perhaps becoming short-tempered, withdrawn, apologetic, or subservient, and the man again reacts negatively, sowing yet another karmic seed.

All has to do with karmic traces:

All samsaric experience is shaped by karmic traces. Moods, thoughts, emotions, mental images, perceptions, instinctive reactions, "common sense," and even our sense of identity are all governed by the workings of karma. For example, you may wake up feeling depressed. [...] There may be a hundred reasons for this depression to occur on this particular morning, and it may manifest in a myriad of ways. It may also manifest during the night as a dream.

In dream, the karmic traces manifest in consciousness unfettered by the rational mind with which we so often rationalize away a feeling or a fleeting mental image. We can think of the process like this: during the day the consciousness illuminates the senses and we experience the world, weaving sensory and psychic experiences into the meaningful whole of our life. At night the consciousness withdraws from the senses and resides in the base. If we have developed a strong practice of presence with much experience of the empty, luminous nature of mind, then we will be aware of and in this pure, lucid awareness. But for most of us the consciousness illuminates the obscurations, the karmic traces, and these manifest as a dream.

Finally:

In dream yoga, this understanding of karma is used to train the mind to react differently to experience, resulting in new karmic traces from which are generated dreams more conducive to spiritual practice. It is not about force, about the consciousness acting imperially to oppress the unconscious. Dream yoga relies instead upon increased awareness and insight to allow us to make positive choices in life. Understanding the dynamic structure of experience and the consequences of actions leads to the recognition that every experience of any kind is an opportunity for spiritual practice.

Dream practice also gives us a method of burning the seeds of future karma during the dream. If we abide in awareness during a dream, we can allow the karmic traces to self-liberate as they arise and they will not continue on to manifest in our life as negative states. As in waking life, this will only happen if we can remain in the non-dual awareness of rigpa, the clear light of the mind. If this is not possible for us, we can still develop tendencies to choose spiritually positive behavior even in our dreams until we can go beyond preferences and dualism altogether.

Ultimately, when we purify the obscurations until none remain, there is no film, no hidden karmic influences that color and shape the light of our consciousness. Because karmic traces are the roots of dreams, when they arc entirely exhausted only the pure light of awareness remains: no movie, no story, no dreamer and no dream, only the luminous fundamental nature that is absolute reality. This is why enlightenment is the end of dreams and is known as "awakening."

According to the sutta below, it is one's state of mind which determines one's quality of sleep and not the comfort of the bed and bedroom.

By eliminating or reducing greed/ lust, hatred/ aversion and delusion, one could improve his or her quality of sleep, and enjoy good sleep as the Buddha does.

From AN 3.35:

“Yes, prince, I slept well. I am one of those who sleep well in the world.

“Well then, prince, I’ll ask you about this in return, and you can answer as you like. What do you think? Take the case of a householder or his son, who lives in a bungalow, plastered inside and out, draft-free, with latches fastened and windows shuttered. His couch is spread with woolen covers—shag-piled, pure white, or embroidered with flowers—and spread with a fine deer hide. It has a canopy above and red pillows at both ends. An oil lamp is burning there, while his four wives attend to him in all manner of agreeable ways. What do you think, prince, would he sleep well, or not? Or how do you see this?”

“He would sleep well, sir. Of those who sleep well in the world, he would be one.”

“What do you think, prince? Is it not possible that a fever born of greed—physical or mental—might arise in that householder or householder’s son, burning him so he sleeps badly?”

“Yes, sir.”

“The greed that burns that householder or householder’s son, making them sleep badly, has been cut off at the root by the Realized One, made like a palm stump, obliterated, and unable to arise in the future. That’s why I sleep well.

What do you think, prince? Is it not possible that a fever born of hate … or a fever born of delusion—physical or mental—might arise in that householder or householder’s son, burning him so he sleeps badly?”

“Yes, sir.”

“The delusion that burns that householder or householder’s son, making them sleep badly, has been cut off at the root by the Realized One, made like a palm stump, obliterated, and unable to arise in the future. That’s why I sleep well.

As Suminda wrote in his answer, eleven benefits of freedom of mind through metta are listed by the Buddha, among them:

"One sleeps easily, wakes easily, dreams no evil dreams."
--AN 11.16

More generally, the Buddha has said he sleeps at ease even in unpleasant circumstances because he abandoned craving, aversion and delusion (AN 3.34).

He also said about monks in training:

"These three things lead to the falling away of a monk in training. Which three? There is the case where a monk in training enjoys activity, delights in activity, is intent on his enjoyment of activity. He enjoys chatter, delights in chatter, is intent on his enjoyment of chatter. He enjoys sleep, delights in sleep, is intent on his enjoyment of sleep. These are the three things that lead to the falling away of a monk in training.

"These three things lead to the non-falling away of a monk in training. Which three? There is the case where a monk in training doesn't enjoy activity, doesn't delight in activity, isn't intent on his enjoyment of activity. He doesn't enjoy chatter, doesn't delight in chatter, isn't intent on his enjoyment of chatter. He doesn't enjoy sleep, doesn't delight in sleep, isn't intent on his enjoyment of sleep. These are the three things that lead to the non-falling away of a monk in training."

-- Iti 3.30

In AN 7.58 the Buddha instructs Ven. Maha Moggallana on how to overcome his drowsiness:

"Well then, Moggallana, whatever perception you have in mind when drowsiness descends on you, don't attend to that perception, don't pursue it. It's possible that by doing this you will shake off your drowsiness.

"But if by doing this you don't shake off your drowsiness, then recall to your awareness the Dhamma as you have heard & memorized it, re-examine it & ponder it over in your mind. It's possible that by doing this you will shake off your drowsiness.

"But if by doing this you don't shake off your drowsiness, then repeat aloud in detail the Dhamma as you have heard & memorized it. It's possible that by doing this you will shake off your drowsiness.

"But if by doing this you don't shake off your drowsiness, then pull both your earlobes and rub your limbs with your hands. It's possible that by doing this you will shake off your drowsiness.

"But if by doing this you don't shake off your drowsiness, then get up from your seat and, after washing your eyes out with water, look around in all directions and upward to the major stars & constellations. It's possible that by doing this you will shake off your drowsiness.

"But if by doing this you don't shake off your drowsiness, then attend to the perception of light, resolve on the perception of daytime, [dwelling] by night as by day, and by day as by night. By means of an awareness thus open & unhampered, develop a brightened mind. It's possible that by doing this you will shake off your drowsiness.

"But if by doing this you don't shake off your drowsiness, then — percipient of what lies in front & behind — set a distance to meditate walking back & forth, your senses inwardly immersed, your mind not straying outwards. It's possible that by doing this you will shake off your drowsiness.

"But if by doing this you don't shake off your drowsiness, then — reclining on your right side — take up the lion's posture, one foot placed on top of the other, mindful, alert, with your mind set on getting up. As soon as you wake up, get up quickly, with the thought, 'I won't stay indulging in the pleasure of lying down, the pleasure of reclining, the pleasure of drowsiness.' That is how you should train yourself.

His last advice above is a general instruction on how to sleep and how the Buddha himself is described sleeping. He also describes elsewhere (AN 4.37) how a monk is "devoted to wakefulness":

"And how is a monk devoted to wakefulness? There is the case where a monk during the day, sitting & pacing back & forth, cleanses his mind of any qualities that would hold the mind in check. During the first watch of the night, sitting & pacing back & forth, he cleanses his mind of any qualities that would hold the mind in check. During the second watch of the night, reclining on his right side, he takes up the lion's posture, one foot placed on top of the other, mindful, alert, with his mind set on getting up [either as soon as he awakens or at a particular time]. During the last watch of the night, sitting & pacing back & forth, he cleanses his mind of any qualities that would hold the mind in check. This is how a monk is devoted to wakefulness.

Monks, eleven advantages are to be expected from the release (deliverance) of heart by familiarizing oneself with thoughts of loving-kindness (metta), by the cultivation of loving-kindness, by constantly increasing these thoughts, by regarding loving-kindness as a vehicle (of expression), and also as something to be treasured, by living in conformity with these thoughts, by putting these ideas into practice, and by establishing them. What are the eleven?

1. "He sleeps in comfort. 2. He awakes in comfort. 3. He sees no evil dreams. 4. He is dear to human beings. 5. He is dear to non-human beings. 6. Devas (gods) protect him. 7. Fire, poison, and sword cannot touch him. 8. His mind can concentrate quickly. 9. His countenance is serene. 10. He dies without being confused in mind. 11. If he fails to attain arahantship (the highest sanctity) here and now, he will be reborn in the brahma-world.

(Mettanisamsa Sutta)