The Jacket by Jack London

One thing of great value I learned in the long, pain-weary hours of waking-namely, the mastery of the body by the mind. I learned to suffer passively, as, undoubtedly, all men have learned who have passed through the post-graduate courses of strait-jacketing. Oh, it is no easy trick to keep the brain in such serene repose that it is quite oblivious to the throbbing, exquisite complaint of some tortured nerve.

And it was this very mastery of the flesh by the spirit which I so acquired that enabled me easily to practise the secret Ed Morrell told to me.