If you want the great and mighty things God has for you, you must get to the root of anger and deal with it. Get rid of the masks and face the things that happened in your life that made you the way you are today. Admit that you can't change by yourself. Until the root is removed, it'll continue to produce one bad fruit after another.
Is all anger sin? No, but some of it is. Even God Himself has righteous anger against sin, injustice, rebellion and pettiness. Anger sometimes serves a useful purpose, so it isn't necessarily always a sin. Obviously, we're going to have adverse feelings, or God wouldn't have needed to provide the fruit of self-control. Just being tempted to do something is not sin. It's when you don't resist the temptation, but do it anyway, that it becomes sin.
A man who is wrathful with us is a sick man; we must apply a plaster to his heart - love; we must treat him kindly, speak to him gently, lovingly. And if there is not deeply-rooted malice against us within him, but only a temporary fit of anger, you will see how his heart, or his malice, will melt away through your kindness and love - how good will conquer evil.
Do not say, "I cannot help having a bad temper." Friend, you must help it. Pray to God to help you overcome it at once, for either you must kill it, or it will kill you. You cannot carry a bad temper into heaven.