I just kept critiquing myself after a negative interaction and trying to figure out why I got angry or frustrated.

This bit really is key.

Some of our emotions are legit. Sometimes someone really did try to screw you over or something. But a lot of times...our feelings are based on assumptions that aren't true, and when you pick at the emotion a bit you start to realize you assumed the wrong thing, or didn't consider something else.

So it's important to critique yourself, and think about what happened, and try to dig down into the true root of the situation, separate truth from fact.

I grew up in an abusive home and generally am laid-back so it's hard to get me angry. I had to learn that in my case, the anger I felt actually was valid and not just something I was blowing out of proportion--most people who talk a lot about anger are approaching from the other angle, and have to learn the opposite, that not everything is worth getting angry about.

But both of us, regardless of our "natural starting point", have to learn how to think about stuff that happened, and ask questions, and try to figure out what happened and why.