Anger, in many spiritual traditions, is seen as an emotion that is even more harmful to the angry person than to the target of the anger. In addition to harming the spirit, prolonged anger is unhealthy for the body.
The answer is not to suppress the anger, but to feel it and then let it go. Here is a meditation/visualization exercise to help you process and release anger before it can turn toxic.
1. Prepare for the visualization by focusing on your breath to quiet your mind.
2. Next, imagine a very deep lake. The surface of the lake is choppy, with the wind whipping up the water into ripples and waves that go off in all directions.
3. Imagine that the person you feel anger towards is like this lake. The things the person did or said that annoyed, frustrated, or disappointed you are like the waves on the choppy surface of the lake.
4. Now imagine that you are going down below the surface of the lake, where it is calm and quiet. The deeper you go, the more peaceful and beautiful the water surrounding you becomes.
5. Imagine that this deep, peaceful part of the lake is like the deeper part of the person who you felt anger towards. The things this person did that irritated you were only on the surface, just as the waves were only on the surface of the lake..
6. Go even deeper down into the lake. Realize that here, at the deepest level, the lake is connected to all the water on the planet -- just as the person who angered you is connected to all other people on the Earth, including you. This is the true essence of the lake, of you, and of all people.
By realizing that the behavior that upset you is only a small part of who the other person is, and by reminding yourself that the other person is a deep spiritual being, like yourself, you can let the anger fade away and regain a sense of peace.