I was talking to a friend of mine who never, ever, ever curses, and while we were speaking, a Category 3 word slipped out. "Oh no! I'm so sorry!" she said, face turning purple. Since I knew that this was not her typical vocabulary and could tell she was mortified that she had said it (to the creator of Bleep! no less), so I didn't judge her because of it. Of course I wouldn't! She slipped. It's legal.
Really - you're allowed to slip and say a bad word every once in a while, I promise! While it can be extremely embarrassing to slip, most people will not judge you based on one if they understand it's not the way you usually speak. (This is why it's important to make it very clear when you do slip that you're extremely sorry and humiliated.) So while you may have to deal with some of the negative effects of cursing, chances are people will be understanding. Really - it's not illegal to slip every once in a while!