The Buddha on fun, play & time management during practice & Dharma work

the Buddha's last words relate imho to this ―All component things must decline and decay. Attain your goal through diligence.‖ (Parinibanna Sutta)

(why "play" /waste time when we know how to practice toward Awakening?)

Here's a sutta (AN 8.80) on grounds of laziness and arousal of energy:

"Monks, there are these eight grounds for laziness. Which eight?

"There is the case where a monk has some work to do. The thought occurs to him: 'I will have to do this work. But when I have done this work, my body will be tired. Why don't I lie down?' So he lies down. He doesn't make an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the first grounds for laziness.

"Then there is the case where a monk has done some work. The thought occurs to him: 'I have done some work. Now that I have done work, my body is tired. Why don't I lie down?' So he lies down. He doesn't make an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the second grounds for laziness.

"Then there is the case where a monk has to go on a journey. The thought occurs to him: 'I will have to go on this journey. But when I have gone on the journey, my body will be tired. Why don't I lie down?' So he lies down. He doesn't make an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the third grounds for laziness.

"Then there is the case where a monk has gone on a journey. The thought occurs to him: 'I have gone on a journey. Now that I have gone on a journey, my body is tired. Why don't I lie down?' So he lies down. He doesn't make an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the fourth grounds for laziness.

"Then there is the case where a monk, having gone for alms in a village or town, does not get as much coarse or refined food as he needs to fill himself up. The thought occurs to him: 'I, having gone for alms in a village or town, have not gotten as much coarse or refined food as I need to fill myself up. This body of mine is tired & unsuitable for work. Why don't I lie down?' So he lies down. He doesn't make an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the fifth grounds for laziness.

"Then there is the case where a monk, having gone for alms in a village or town, does get as much coarse or refined food as he needs to fill himself up. The thought occurs to him: 'I, having gone for alms in a village or town, have gotten as much coarse or refined food as I need to fill myself up. This body of mine is heavy & unsuitable for work, as if I were many months pregnant. Why don't I lie down?' So he lies down. He doesn't make an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the sixth grounds for laziness.

"Then there is the case where a monk comes down with a slight illness. The thought occurs to him: 'I have come down with a slight illness. There's a need to lie down.' So he lies down. He doesn't make an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the seventh grounds for laziness.

"Then there is the case where a monk has recovered from his illness, not long after his recovery. The thought occurs to him: 'I have recovered from my illness. It's not long after my recovery. This body of mine is weak & unsuitable for work. Why don't I lie down?' So he lies down. He doesn't make an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the eighth grounds for laziness.

"These are the eight grounds for laziness.

"There are these eight grounds for the arousal of energy. Which eight?

"There is the case where a monk has some work to do. The thought occurs to him: 'I will have to do this work. But when I am doing this work, it will not be easy to attend to the Buddha's message. Why don't I make an effort beforehand for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized?' So he makes an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the first grounds for the arousal of energy.

"Then there is the case where a monk has done some work. The thought occurs to him: 'I have done some work. While I was doing work, I couldn't attend to the Buddha's message. Why don't I make an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized?' So he makes an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the second grounds for the arousal of energy.

"Then there is the case where a monk has to go on a journey. The thought occurs to him: 'I will have to go on this journey. But when I am going on the journey, it will not be easy to attend to the Buddha's message. Why don't I make an effort beforehand for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized?' So he makes an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the third grounds for the arousal of energy.

"Then there is the case where a monk has gone on a journey. The thought occurs to him: 'I have gone on a journey. While I was going on the journey, I couldn't attend to the Buddha's message. Why don't I make an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized?' So he makes an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the fourth grounds for the arousal of energy.

"Then there is the case where a monk, having gone for alms in a village or town, does not get as much coarse or refined food as he needs to fill himself up. The thought occurs to him: 'I, having gone for alms in a village or town, have not gotten as much coarse or refined food as I need to fill myself up. This body of mine is light & suitable for work. Why don't I make an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized?' So he makes an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the fifth grounds for the arousal of energy.

"Then there is the case where a monk, having gone for alms in a village or town, does get as much coarse or refined food as he needs to fill himself up. The thought occurs to him: 'I, having gone for alms in a village or town, have gotten as much coarse or refined food as I need to fill myself up. This body of mine is light & suitable for work. Why don't I make an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized?'1 So he makes an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the sixth grounds for the arousal of energy.

"Then there is the case where a monk comes down with a slight illness. The thought occurs to him: 'I have come down with a slight illness. Now, there's the possibility that it could get worse. Why don't I make an effort beforehand for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized?' So he makes an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the seventh grounds for the arousal of energy.

"Then there is the case where a monk has recovered from his illness, not long after his recovery. The thought occurs to him: 'I have recovered from my illness. It's not long after my recovery. Now, there's the possibility that the illness could come back. Why don't I make an effort beforehand for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized?' So he makes an effort for the attaining of the as-yet-unattained, the reaching of the as-yet-unreached, the realization of the as-yet-unrealized. This is the eighth grounds for the arousal of energy.

"These are the eight grounds for the arousal of energy."

AN 8.80

The previous sutta is related:

“These eight things lead to the decline of a mendicant trainee. What eight? They relish work, talk, sleep, and company. They don’t guard the sense doors and they eat too much. They relish closeness and proliferation. These eight things lead to the decline of a mendicant trainee.

These eight things don’t lead to the decline of a mendicant trainee. What eight? They don’t relish work, talk, and sleep. They guard the sense doors, and they don’t eat too much. They don’t relish closeness and proliferation. These eight things don’t lead to the decline of a mendicant trainee.”
AN 8.79

Regarding play (SN 23:2):

“Any desire, passion, delight, or craving for consciousness, Rādha: when one is caught up there, tied up there, one is said to be ‘a being.’

“Just as when boys or girls are playing with little sand castles (lit: dirt houses): as long as they are not free from passion, desire, love, thirst, fever, & craving for those little sand castles, that’s how long they have fun with those sand castles, enjoy them, treasure them, feel possessive of them. But when they become free from passion, desire, love, thirst, fever, & craving for those little sand castles, then they smash them, scatter them, demolish them with their hands or feet and make them unfit for play.

“In the same way, Rādha, you too should smash, scatter, & demolish form, and make it unfit for play. Practice for the ending of craving for form.

“You should smash, scatter, & demolish feeling, and make it unfit for play. Practice for the ending of craving for feeling.

...

However, the Buddha did speak of the pleasure of concentration, and of the contentment of a developed mind.

Regarding time management:

It is an abstract concept, power propaganda, designed to funnel thinking and effort in a certain direction. The Buddha spoke of other things, things conducive to ending suffering. Like skill, heedfulness, harmlessness... These sorts of things are what should inform all of our decisions.