Depends who I'm with. I have a nasty habit of swearing too much, but thankfully I can turn it on and off at will. I sometimes swear like a trooper, and others times I use the "holy cow"'s and "tough luck"'s.
I'm always careful that I know who I'm swearing like a trooper around though. Once I know whether someone is offended by swearing or not, than I can decide whether to let the expletives fly.