Couldn't sleep

Last night I lay awake for several hours, thinking about some things that had happened a year or two ago and getting very angry about them. I was so angry I couldn't possibly sleep. I just kept going over the events in my mind, over and over, thinking of different ways I could have stood up for myself or ways I could have made things turn out differently.

Why was I so angry? Sure, these things would probably tick off a lot of people, but that was then -- why am I so angry now, more than a year afterward? Why am I still carrying this around? Is it because I'm mad at myself for not sticking up for myself or for not somehow showing my anger at the time?