I struggled when first ill and do still now to some extent with anger. Most of it is actually justifiable anger. I mean anger in response to moral evil or situational abuse and a feeling of powerlessness in response.
Basically though, I found a counselor that let me just express it all and talk about it and I talk to myself about it too, about why I am angry and I write about it too.
Finding out WHY the anger and then finding positive ways to work out the issue is helpful to me. Not all problems are solvable so then it becomes dealing with the feelings, the emotions so that I am not hurt by my own anger.