I wouldn't say I was 'tormented' by negatives, although they do crop up in my mind from time to time... how I could've handled a situation better, or a witty retort that I wish I'd thought of at the time, or what if I'd done this or that.
Sometimes it's mulling over something trivial: for instance, trying to read a book, and instead of focusing on the words on the page, I'm being distracted by a part of the brain that says stuff like 'hey Dan, remember that time about 14 years ago when you got a bit too drunk, went to a nightclub and danced like a tit, asked the police to give you a lift home and then turned up at your friend's flat at 3am wanting to sleep on the floor? Remember that? What an idiot you were, eh? Just keepin' that memory alive. Anyway, you better read that paragraph again, I don't think you've taken it in.'