All the time. I'll check for spelling errors, grammar errors, "oh wait this sentence sounds weird", start over, check this, check that, "no I feel dumb saying it like this", start over...
There's a reason I can't post fast like some people. I spend too much time mulling over things and making sure I have it just right or close enough to it that I'm satisfied. It's kind of annoying at times, actually. :(