In reply to Anonymous.

If I don't fold, will you then fold thinking I have a good hand? If so, that is music to my ears and I can't wait to play with you.

If I tell you I am bluffing, am I?

Seriously though, there is a point in a hand where you might realize you have no chance in winning. ie flop sucks, you don't hit the flush or straight, or any other of a million hands. Sure I may have committed a portion of my chips to the pot, but if I have no way of winning, I can try to bluff or fold.