Here's how to study, and how (when the time comes) not to:
If you want really to do your best in an examination, fling away the book the day before, say to yourself, “I won’t waste another minute on this miserable thing, and I don’t care an iota whether I succeed or not.” Say this sincerely, and feel it; and go out and play, or go to bed and sleep, and I am sure the results next day will encourage you to use the method permanently. William James, “Gospel of Relaxation"
It is needless to say that that is not the way to do it. The way to do it, paradoxical as it may seem, is genuinely not to care whether you are doing it or not.