I don't think it's depression

But i bet it could be treated in a similar way. I donno, I have a book on depression that suggests that whenever you have a depressing thought (or in ur case an angry thought) you write it down and then write down a rebuttle. I guess, a reason to not get angry. You have to keep trying to veiw the situation from a different and less negative angle. But you have to actually write it down, not just do it in ur head.
The theory is that emotions are caused by what you say/think to yourself, not by what actually happens, so if you practice thinking well and rationally you can end up feeling a lot better^_^
Try looking up info or finding a book that has a section on the "cognitive traps". Well, that's what my books calls them, they probably have different names tho... Cognitive distortions, errors, etc...
Anyways, good luck!