I've been on the recieving end of a little bit of this CBT stuff - trying to stop the negative tape that constantly plays. The psych I saw told me that rather than be overwhelmingly positive in my thoughts (because that can set up just as unrealistic an expectation at the negative thoughts) I needed to practice a realistic way of thinking. For example, telling myself I'm stupid is wrong (and a lie, I'm not). Telling myself I'm brilliant and worthy of Mensa is also wrong. So I should go with something along the lines of I'm intelligent and articulate and have skills I can use to achieve what I want, but I also make mistakes.

Those hormones are a pain in the arse though, aren't they? :)