Oh, all the time. Sometimes I write a whole wall of text, then realise that what I've been saying doesn't make sense, or that it's not interesting, or anything like that. I swap out the somewhat odd post with a single sentence stating my opinion on the matter, and leave it at that. More frequently on threads about objective matters than on ones of opinion, but maybe that's just me. Well, sometimes on matters of opinion, but only if I'm partway through a massive post and then it occurs to me that I have no real reason to waste my time writing up said post.
No, not really.