Phil Gordon says you have to know when you can’t win.

Gordon:    One of the things that I think has really contributed to my success in business and in poker is something that one of the great players taught me, right when I first started playing, and that was pretty simple.  When you’re losing, make any excuse you can find to get up from the table and leave, and when you’re winning, plant your ass in the seat and make them come after you.  Basically, it works because when you’re winning, they’re chasing their losses.  They’re probably playing sub optimally.  You’re probably playing at the best of your game, and even if you’re not, they might think you are.  When you’re losing, there may be multiple reasons that you’re losing.  They can be playing very well, you can be playing poorly, you could not have focus, but I think that, you know, one of the guys that truly believes that if you’re losing you make any excuse necessary and you get up and you go home and you save it for another day, but if you’re winning, it’s almost impossible to get me up from the table.