Robert Greene said this quote
“ Understand: your mind is weaker than your emotions. But you become aware of this weakness only in moments of adversity,precisely the time whenyou need strength. What best equips you to cope with tthe heat of battle is neither more knowledge nor more intellect. What makes your mind stronger, and more able 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 first step in building up presence of mind is to see the need for it, to want it badly enough to be willing to work for it. ”