The Enchiridion (47)

When you have learned to nourish your body frugally, do not pique yourself upon it; nor, if you drink water, be saying upon every occasion, I drink water. But first consider how much more frugal are the poor than we, and how much more patient of hardship. If at any time you would inure yourself by exercise to labor and privation, for your own sake and not for the public, do not attempt great feats; but when you are violently thirsty, just rinse your mouth with water, and tell nobody.