You're kind hearted and all that good stuff, but it's not always easy for you to just let certain things roll off your shoulders. And by "certain things", I mean when someone crosses the line with you. This is when the "claws" come out.
Your frustration mounts pretty quickly when you're in the heat of the moment. By this point, thinking logically is not your strong suit. You tend to think about all the messed up things that may be going on in your life at that time, so it fuels your anger.
You even black out from being so angry! (lol. This has never happened to me... yet.) But in the end, you bounce back and life goes on.