This is one of the basic rules of poker, but one that is - for some reason easily overlooked or forgotten. If you’re beat, fold. And listen to that little voice telling you that you are beat. (We often hear players at the table tell us, «I know I’m beat» - as they continue to toss in the chips.)
Hanging on (and on, and on) in a hand is where a lot of the money goes.
“You always told me this was … rule number one: Throw away your cards the minute you know you can’t win. «Fold the f–hand…» - Kevin Canty, Rounders
Also, forget the idea that they’re bluffing or trying to «run you out.» You’re almost always better off folding. Most of the time they do have something. (Or at least this is true enough of the time to justify folding on your part.) Generally speaking, when things start to go wrong in your hand, you’re better off exiting the hand. Don’t hang around hoping and wishing («I’II see one more card … and one more … and one more …»). Meanwhile, other players are betting and raising with a «made hand». Unless you are up against players who deliberately make moves of this kind (to try to force you out), it is never a bad idea in poker, at the first sign of trouble, to get away from the hand.