The Arizal was more concerned about anger than any other sin, even when the anger was for a mitzvah. He explained that every sin damages a limb, whereas anger damages the neshamah and totally changes it. When a person becomes angry, his neshamah departs from him and in its stead enters a soul from the realm of evil. This is what is meant by, “He kills his soul with his rage”—he literally kills his holy soul with his rage, as is explained in the Zohar.
