I agree with HLT, but your anger evaluation is too simple.

There are so many different things that can lead to anger. Many different causes which might have nothing to do with your expectation. Often it also happens that the first thing that comes to your mind that you think is making you angry is not the real reason. Builtup frustration and stress can lead to being angry at anything at anytime.

As you can see, always reexamining your expectations might not work.