Don't Stay in a Hand Just Because You're Already In It
Another common mistake beginners make is to think that "Well, I've already put that much in the pot, I have to stay in now." Nope. You can't win a pot just by throwing money at it. There may be cases when pot odds warrant a call, but if you're sure you're beaten, and there's no way your hand can improve to be the best hand, you should fold right away. The money you've already put in the pot isn't yours anymore, and you can't get it back just by playing a hand all the way to the end.
