While there can be many reasons for falling ill, especially in the case of a serious student of Yoga, one of the reasons is this inability of the body to adjust itself suddenly to a very strong thought which is quite different from the usual thoughts of individuals that we are familiar with. Because, when the seeker takes to Yoga, he is likely to be stirred up into an emotion of holiness and religiosity, which may lead him to think of such items of exceptional practice as fasting, reducing one's sleep, eating less, talking nothing and so on. While all these practices are very advantageous, and perhaps necessary, they should not be resorted to all at once, in an extreme measure. Moderation is a greater virtue than complete abstention. Complete abstention may not be so difficult as moderation.
Moderation is more difficult.
For instance, to speak in a moderate and acceptable manner poses a greater difficulty for a person than to observe complete Mauna or silence. Yoga is, a moderation of conduct and an internal adjustment. It is not an extreme step that one takes, though sometimes an individual seeker goes to extremes unavoidably due to his very nature. That is why we run to monasteries and sequestered places. No human individual can escape this eventuality of being stirred inside in a holy manner, which may look like something extreme to the poor body which is not used to these conditions of thinking and feeling.