Karma, right effort, letting go, heroic sacrifices: what's the right thing to do?

The teaching that the string on the stringed musical instrument must not be too taut or too loose, but it should be tuned precisely, is taught in the Sona Sutta. The middle path is also expounded in the Dhammacakkapavattana Sutta (below) and discussed in this answer. I believe that the Buddha was very firm on the middle path teaching.

"Monks, these two extremes ought not to be practiced by one who has gone forth from the household life. (What are the two?) There is addiction to indulgence of sense-pleasures, which is low, coarse, the way of ordinary people, unworthy, and unprofitable; and there is addiction to self-mortification, which is painful, unworthy, and unprofitable.

"Avoiding both these extremes, the Tathagata (The Perfect One) has realized the Middle Path; it gives vision, gives knowledge, and leads to calm, to insight, to enlightenment and to Nibbana. And what is that Middle Path realized by the Tathagata...? It is the Noble Eightfold path, and nothing else ...

However, you found the story of Cakkhupāla Thera which is here and here. You have got the story right, but I think you have misinterpreted the Buddha's reply as to why Ven. Cakkhupāla is blind despite being an arahat.

The Buddha said "As a result of this evil deed the physician lost his eyesight many times in his later existences." He did not say, "he did not take his medicine in this life and therefore became blind due to his past karma". Ven. Cakkhupāla definitely had the free will to accept or reject the medication, and this is not impaired by his past evil deed.

On the other hand, we can say that he contracted the eye infection due to his past evil deed. If he had taken the medication, we still do not know whether he would end up cured or blind. Even if he was cured, he might still become blind later. Hence, there is no relationship between his decision to not take the medicine and his past evil deed.

Ven. Cakkhupāla's decision to not take medication, could be considered a form of self-mortification which may or may not be related to him achieving Nirvana. The Buddha did not comment about this. He only commented on how the arahat could be blind - the reason is his past deeds. And this only explains why he contracted the eye infection in this life.

Furthermore, the Buddha says that not everything that we experience is the result of our past karma, in the Sivaka Sutta (below) and also discussed in this answer. Hence, Ven. Cakkhupāla rejecting his medicine or Gautama choosing to search for enlightenment is not completely the result of their karma. They had their own free will too, in their last lives. It is only that Gautama's past karma contributed towards his strong inclination towards enlightenment but did not absolutely fate him to it.

"There are cases where some feelings arise based on phlegm... based on internal winds... based on a combination of bodily humors... from the change of the seasons... from uneven care of the body... from harsh treatment... from the result of kamma. You yourself should know how some feelings arise from the result of kamma. Even the world is agreed on how some feelings arise from the result of kamma. So any brahmans & contemplatives who are of the doctrine & view that whatever an individual feels — pleasure, pain, neither pleasure-nor-pain — is entirely caused by what was done before — slip past what they themselves know, slip past what is agreed on by the world. Therefore I say that those brahmans & contemplatives are wrong."

Yes, there may be stories of Buddhist monks who did not take care of their health or practised extreme ways in pursuit of enlightenment. But this does not meet Buddha's teaching of the middle path. The Vinaya rules laid down by the Buddha for monks, allows monks to have meals before noon daily, and also allows monks to take medicine at any time of the day for their illnesses. Hence, we must accept that this is inline with Buddha's middle path teaching, as laid down for monks.

The will and determination to achieve enlightenment can be strong but the middle path should still be followed. How would music be created, if the string is too taut or too loose?

Great Question Buddho!

It is true, the middle way is always the best way. I think your understanding of Karma however may be slightly off the mark. This can all be explained in terms of qualities and quantities. The monk who lost his eyes in replace for the vision of enlightenment seems slightly absurd, losing your eyes due to bad karma however can be the case. Here is why: If this person committed a terrible deed in their last life of lets say gauging someone's eyes out it would seem fitting that they lost their eyes in that life or the next. The bad karma however is not so Solid! If this person in the next life worked very hard to do good things for people and the earth than they could attain enlightenment without losing their eyesight! If they live a quite a good life but still have defilements this person might get cataracts instead of losing their eyes. If however, this person lives a life with no intention to remove defilements than they may very well lose their eyes. Does this make a man who sits for so long that he loses his eyes an enlightened being? Surely not. Meditation is helpful for gaining insight, better concentration, patience and contentment which are all good qualities. But if you want to generate good karma and in doing so remove bad karma, than you must work hard to improve the beings and planet around you. Buddhists refer to karma as 'action' and because 'action' is happening all the time than 'your' action or 'your' karma is also happening all the time. Work hard to do good and you will become a good karmic being, regardless of your passed sins. The only variable that you have to be concerned with is the weight of your passed sins, if they are heavy like killing than you will have to work extremely hard to redeem yourself. This is opposed to people who don't have heavy sins, and so your bad karma will need to be overthrown by your good karma before you are to achieve enlightenment. But you certainty don't have to lose your eyesight in order to do so! Hope this helps :)

"Isn't there a story where the Buddha accosts a monk who's bleeding from performing walking meditation for too long, and tells him practice must be like a Veena's string - not too tight, not too loose? i.e the middle way"

The string story is in AN 6.55.

"Yet, I remember a story in the Dhammapada (Verse 1) about a monk who refused to take his eye medicine because he had vowed to not lie down for three months and remain practicing full time. Since the medicine wasn't effective unless taken lying down, he lost his eyes. The text says he simultaneously lost his vision and gained his vision - i.e. he became an arahant by practicing so arduously."

It seems this story is not described in Dhammapada, but in a commentary? I could not find a full text of it.

"The Buddha peeks into his past lives, and says Karma dictates that he must lose his eyes in this lifetime for sins of the past."

I've never found this kind of wording in any sutta: "karma dictates" or "because of karma, he must". Describing karma in this way is not only at odds with the actual karma doctrine taught by the Buddha, but he also criticized the idea that "karma dictates": it would be impossible to anyone to live the holy life, become an arahant, become a Buddha, if that was the case.

"Leaving everything to Karma has me confused - because if that is so, then why practice, even enlightenment if it is in our karma will be obtained without effort. Gautama the Buddha was certainly going to become a Buddha, his Buddhahood had been foretold, so why did he practice?"

The questioning above is similar to the way the Buddha often debunked this very idea.

"Monks, for anyone who says, 'In whatever way a person makes kamma, that is how it is experienced,' there is no living of the holy life, there is no opportunity for the right ending of stress. But for anyone who says, 'When a person makes kamma to be felt in such & such a way, that is how its result is experienced,' there is the living of the holy life, there is the opportunity for the right ending of stress.

-- AN 3.99

A book I would suggest here is Good, Evil and Beyond: Kamma in the Buddha's Teaching (besides the suttas where karma law is taught).

"Second, what's with the open praise of macho effort right at the start of the Dhammapada? What happened to the middle way?"

It's less about macho, and more about determination.

Also "middle way" does not mean avoiding anything one may personally consider to be "extreme". When this denomination is used by the Buddha, he is either talking about avoiding specific sterile and false/incorrect extremes:

"There are these two extremes that are not to be indulged in by one who has gone forth. Which two? That which is devoted to sensual pleasure with reference to sensual objects: base, vulgar, common, ignoble, unprofitable; and that which is devoted to self-affliction: painful, ignoble, unprofitable. Avoiding both of these extremes, the middle way realized by the Tathagata — producing vision, producing knowledge — leads to calm, to direct knowledge, to self-awakening, to Unbinding.

-- SN 56.11

...or explaining how this is his strategy of teaching:

"'Everything exists': That is one extreme. 'Everything doesn't exist': That is a second extreme. Avoiding these two extremes, the Tathagata teaches the Dhamma via the middle: : From ignorance as a requisite condition come fabrications ...

-- SN 12.15

"This is not an isolated instance, there are several stories about heroic efforts from monks. The most famous must be the version where Bodhidharma plucks out his eyelids. There's also another version where he loses his legs to atrophy by not moving for nine years."

Though Zen has the habit of increasing the dramatic effects a noch, still, it's how determination is conveyed. Underlying this intense determination is a sense of urgency, often produced by an experience of insight into the dhamma.

So, it's not about heroism -- not in the western sense. Nor about sacrifices. The kind of sacrifices praised by the Buddha are sacrifices of unwholesome acts of body speech and mind. Are sacrifices related to the household life, and so on.

It was pointed out that physical pain may significantly affect one's mind in a karmic way. But mostly as an explanation of the law of karma, not as a practice to be undertaken -- that is, to inflict pain in oneself. (I don't remember the sutta, unfortunately; it's a passage where the Buddha says someone who undergoes a lot of pain may find him/her self reappearing in a better realm because of that).

"I got to thinking about this after reading this question about monks and exercise. I am reminded of "A path with heart", by Jack Kornfield, where the author, himself a Buddhist monk under Ajahn Chah for several years talks about exercise and several other normal healthy things monks ignore in order to pursue enlightenment single mindedly. He recounts interviewing several monks who suffered from diabetes and other lifestyle diseases that came from not eating healthy food, from not exercising, from developing an aversion to their body and consequently not caring enough."

As far as their body negligence, from the point of view of Buddhism (and of the path to Nirvana) these monks are blameless or not depending on their intention. The bodily pain (or what one could see as a "sacrifice") produced by these health disorders alone is not necessarily praiseworthy or blameworthy -- though it could present itself as an obstacle which could have been avoided. Finally, their suffering depends on their skill and maturity.

I want to say something, not about karma but about doing it now.

The middle way notwithstanding, perhaps it was essential to the Buddha's own enlightenment. I don't know in which sutta this appears, but this narration of the life of the Buddha by Bikkhu Bodhi says,

Now he was alone, and complete solitude allowed him to pursue his quest undisturbed. One day, when his physical strength had returned, he approached a lovely spot in Uruvela by the bank of the Nerañjara River. Here he prepared a seat of straw beneath an asvattha tree (later called the Bodhi Tree) and sat down cross-legged, making a firm resolution that he would never rise up from that seat until he had won his goal. As night descended [etc.]

Thiago's answer says something about Zen and 'urgency'. That 'urgency' reminds me of a word I like, 'akalika' which meaning 'timeless' means immediately, without delay, continuous and eternal (and the absence of kalika).

Anyway, maybe the following is a Zen story which helps to illustrate: Three Days More