This quote about professional baseball struck me as incredibly relevant to starting a business. The best entrepreneurs are those that are in control of their emotions, and are perhaps a bit crazy.

"The point about Lenny, at least to Billy, was clear: Lenny didn't let his mind screw him up. The physical gifts required to play pro ball were, in some ways, less extraordinary than the mental ones. Only a psychological freak could approach a 100-mph fastball aimed not all that far from his head with total confidence." Lenny was so perfectly designed, emotionally, to pay the game of baseball," said Billy. "He was able to instantly forget any failure and draw strength from every success. He had no concept of failure. And he had no idea of where he was." Page 46 of Money Ball.