I sometimes play dumb when somebody calls me a donk or fish or whatever. There are definitely times when my bluff has failed miserably, making me look like a donk. I'll respond stupidly pretending that it wasn't a bluff and that I dumbly thought my hand was good. If the believe me and think of me a a total idiot, they will respect my bets much less and I can get callers when I hit a monster hand.