It is not God's will that you carry anger in your heart. When you are angry, just like at any other time in your life, you need to pray. Praying when you are angry gives you a chance to vent your anger to God. God is big enough to accept your anger. God is also loving enough to help you restore you heart to a state of peace and calm after you and the Lord have spoken about what has made you angry.
Anger is the most dangerous of emotions.
If you do not take your anger to God, then Satan is more than willing to use your anger to hurt others and hurt you. When you are angry, go to God, express your anger, and let God work on you and in you. It is important that you do not leave the presence of the Lord until your anger has subsided. It is especially important to go to the Lord when you are angry with Him. He knows all about your life.