The three biggest mistakes people make are:
1. Playing too many hands. This mistake alone automatically generate two more mistakes:
2. Calling too much by the showdown, and
3. Folding too much before the showdown
So, if you make the mistake #1 of playing too many hands, you will get yourself in an untenable position. Just because you know there is a fairly good chance that you have your opponent beaten early in the hand does not mean you should call his bet. You can’t stop more cards from coming. And if your hand has little chance to improve significantly, you may very well be in an untenable situation. Namely one where your only hope is that you have the best hand now and that it stands up. Not taking into account the possibility your opponent can draw out on you as well as have you beat already will have you playing many hands you should throw away. For instance, if your hand has a thirty percent chance of being best now, but there is a one-third chance he will improve his losing hand to a winning hand, your actual chance of winning the pot is 20%.