Understand: your mind is weaker than your emotions. But you become aware of this weakness only in moments of adversity--precisely the time when you need strength. What best equips you to cope with the heat of battle is neither more knowledge nor more intellect. What makes your mind stronger, and moveable to control your emotions, is internal discipline and toughness. No one can teach you this skill; you cannot learn it by reading about it. Like any discipline, it can come only through practice, experience, even a little suffering.

The 33 Strategies of War