If the bad beat knocks me out of the tournament I laugh it off... I've always been happy when I lose from a winning position because I know I got my chips in at the right time while I was ahead and there's nothing you can do about being outdrawn or someone hitting runner runner...
If I take a bad beat but am still in the game, I shake my head, take a deep breath or two and just wait for another opportunity to start climbing the ladder again...
Usually when I get knocked out I say 'It's a s**t game' to vent my frustration, but I never mean it and it's more of a joke really... I'll always be back.