Our sages say: "He who gets angry is like an idol worshipper". We can understand that losing our temper is ineffective and detrimental to our personal growth. But comparing anger with idolatry seems a little overboard and harsh. Why is it so severe?
Idolatry is considered a severe transgression because it denies the foundation of Jewish belief. At the core of our belief system is that G-d not only created all of existence but that He continues to be in absolute control of everyone and everything. A logical extension of this belief is that all that takes place is by Divine providence - a principle that makes it easier to accept whatever happens to us, even when it is unpleasant. The only thing that G-d allows us to control is our own moral decisions and emotional responses.
Idolatry suggests that there are multiple entities or authorities that control the world's destiny. It goes against the fundamentals of our faith, thereby weakening our commitment to G-d, His commandments and the values of the Torah.
When we lose our temper we are making a statement. We are saying that we cannot accept what has just occurred. We have not been able to control our experiences and find that difficult to deal with. On the other hand, acknowledging Divine providence allows us to act responsibly without getting angry.
Besides being a damaging experience emotionally, rage represents an erosion of our belief system. For this reason the sages compare anger to idolatry.
If we remember one simple rule we can learn to control our temper: We cannot control anything that happens around us, but we can control how we respond.