I curse in my head.
More than I'm proud of, to be honest. Obviously, it's most desired to avoid cursing in your thoughts, but as long as they don't come out of your mouth, there's nothing wrong with it. Bleep!'s reasoning behind not cursing is because people will judge you and everyone and everything that you represent poorly. If you think bad words, no one can hear them - they certainly can't judge you based on what they can't hear!