We all have this idea of how things should be.
How they should go.
We play them over and over in our minds.
When events fail to live up to our expectations, what happens: anger.
Expectation, our future-self-projection, is almost always (maybe always, I can't think of any other cause) the root of anger.
I have heard it said that an angry person is a truthful person. That this is when a persons true feelings and sentiments come out.
I disagree. Anger is a beast, a demon, it is not you. Anger only wants to consume and destroy.
In my own experience, angry, what I want is to bring everything down around me. To lash out and hurt. To destroy.
Doing these things feeds the Anger like a flame. And like a flame untended it will consume everything in its path.
So how do we not succumb to this beast that lies within?
Managing expectations is a good start.
Managing our view. Reality can be harsh, and this is why a lot of times we don't dwell in it or on it in a positive way. But if we can learn to see things as they are, our expectations will follow.
Don't be selfish. Everyone is not out to get you, but they're probably not out to help you, either. It's hard being a human, there are a lot of things we have to do, and a lot more we want to do. What works best for me is setting my mind that I play a supporting role in this life: and I'm good at it. That's not an easy mindset to maintain, but it can be rewarding (and this means the spotlight is on someone else, so less pressure!).
Be healthy. This is such a basic thing to accomplishing everything in your life. Taking care of ourselves can be broken down to these four things: Sleeping well, Eating well, Moving well, and Thinking well. We have some level of control over all of that. Manage it.
Of course, not having expectations in the first place is ideal. Then we experience life and its events as they are and not through a biased lens. But this is no easy task. Work on the rest, and maybe this will follow.
Good luck.
And don't feed the beast.