This is good advice, it's hard as hell to follow but it's good advice. I have the same problem with taps in my head, repeating the same litany of negative commits. Another thing you can do besides just trying to stop think about it is try to make a positive tape as it were. Find some good qualities in you or some things you are proud of and talk to yourself about them. It helps if you have other people telling you positive things too but that's not really something we can control to well. You might tell your friends that you are having a hard time and some positive encouragement and complements would be helpful.

Do things that give you a since of accomplishment and make sure to tell yourself that you did a good job. Something that can be really helpful is doing kind acts for other people. People are social animals and when that monkey part of your brain thinks you are building up your social rank by being helpful to others it makes you happier. That's part of the reason some people volunteer all the time, they get physical pleasure from it and it boosts their ego.