Thesis is that anger is the result of a cascade.
Expectations -> Disappointment -> Resentment -> Blame -> Anger
(From memory, will update if needed.)
So the trick is update one's expectations, short circuit the cascade before it can even start.
Separately, I learned that we can only replace habits with new habits, vs unlearn habits. Completely out of ideas, I faked being happy. One day I woke up, said to myself "Phenomenal!", and truly meant it. I was shocked that it worked. My whole transformation took about three years. YMMV. (Maybe having a life coach would work faster.)
McKay's book When Anger Hurts got me onto the right path. https://www.amazon.com/When-Anger-Hurts-Quieting-Within/dp/1... TLDR: Anger starts with expectations. Which leads to disappointment, resentment, blame, and then lands on anger. I keep hoping for followups; surely the state of the art has progressed since.
The next plateau for me was figuring out how to unlearn my anger habit. I heard that habits can only be replaced. So I decided to pretend being happy, positive. Why not? Nothing else worked and I was out ideas.
I was really surprised that it worked.
Next plateau for me was dealing with anxiety. Maybe half of my symptoms had a physiological origin. Only discovered after a lumbar fusion and my anxiety was mostly gone. In retrospect, I'm grumpy for all the wasted effort and misc treatments endured (eg SSRIs).
I still don't have much clue about dealing with trauma, PTSD. I'd like to try psychotropics (shrooms, MDMA), but have had trouble finding trustworthy suppliers.
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Thanks to u/Dowwie for Bone's Feeling Good tip. Somehow hadn't seen that before. Will try it.
The other half of the solution is to short-circuit anger, prevent it from even happening.
When Anger Hurts https://www.amazon.com/When-Anger-Hurts-Quieting-Within/dp/1...
TLDR: expectations -> disappointment -> resentment -> blaming -> anger
So the trick is to change your expectations. Not eliminate or lower, exactly. But figuring out how to have realistic expectations. Which stops the anger cascade before it can start.
YMMV. Good luck.