I judge myself really harshly too. But I tell myself that if I've said something stupid, other people won't be dwelling on it like I will, and most likely people won't even remember it.
I can't deal with arguments, I'm very sensitive to negativity. I get way more upset by it than I should.
I could try to come up with some explanation, like, people use humor as a defense mechanism to deal with social anxiety . . . but probably I just enjoy goofing around. Especially when I get the feeling that I'm among like-minded people (like in this thread ).
I often find it difficult to express my thoughts, so . . . +1 to the bolded part.