Rebbe Nachman of Breslov tells us that anger is an overbearing obstacle to psycho-spiritual growth and understanding. In Likutey Eitzos (Collected Advice), the Rebbe says:
Anger and unkindness arise when people’s understanding is limited. The deeper their understanding the more their anger disappears, and kindness, love and peace spread. This is why the study of Torah, which deepens the understanding, brings love and peace into the world and banishes anger.
Anger finds it’s roots in a variety of flawed beliefs and feelings about God, the World, other people, and yourself.