The other thing his teammates came to realize was that he was driven by an almost unparalleled desire—or need—to win.
He simply hated to lose, on the court in big games, on the court in little games, in practice, in Monopoly games with his friends. In card games and pool games, his passion to win was obvious—in fact, he often seemed to change the rules to ensure his victory.
He simply hated to lose at anything, and this would be a trademark for the rest of his life. Every competition had a quality of life-or-death struggle. If he lost in a card game, he would want to keep playing until he won.
From "Playing for Keeps" by David Halberstam