chefsnoopy has it right about the long run being what matters. Too many players focus on short-term results, all the wau down to a single hand. They lose one on which they're say an 80% favorite, and they get angry or even go on tilt. They forget that 80% means - in the long run - losing 20% of the time in that situation, which - also in the long run - is very profitable. Poker is about doing the right thing, which you can control, not one-time results, which you can't.