In general, any methods of discipline applied to the body which tend to modify its desires or repulsions, are good--for ascetic ends.

But if done for display, they betray at once a man who keeps an eye on outward show; who has an ulterior purpose, and is looking for spectators to shout, "Oh what a great man!"

This is why Apollonius so well said:

"If you are bent upon a little private discipline, wait till you are choking with heat some day--then take a mouthful of cold water, and spit it out again, and tell no man!"