People usually think of anger as a negative, and they should. However anger in itself is not a sin. "Be ye angry, and sin not: let not the sun go down upon your wrath (Ephesians 4:26)." God gets angry, and He cannot sin. There are two major differences between when God gets angry, and when we get angry. God gets angry over the sin of man, not over the inconveniences and irritations of this life. God does not stay angry (Psalm 103:9), especially when we repent. The anger of God can be appeased when we pray (Exodus 32-33, Numbers 14, Joel 3, Amos 7:1-6). Men of God such as Moses, David, and Paul sometimes got angry. Even Jesus got angry (Matthew 23, Mark 3:5, John 2:13-17). It is unrealistic to get a goal of never getting angry. A realistic goal is to control anger, and to strive to avoid sinning with anger. It can even be channeled as a short term motivation to good as Samuel and Jehu did (1Samuel 11:6, 2Kings 9:20). Their problem was they did not understand that good cannot be sustained very long by anger. They used anger to get started, but they never moved from anger to purpose, and they both failed to accomplish the will of God in the long term. The Bible describes anger as being kindled 40 times. Anyone, who has builds campfires knows that you need kindling to get fire started. Kindling burns hot and fast, but not long. You need more substantive pieces of wood to grow and keep a real fire. Uncontrolled anger leads to evil (Proverbs 14:17, Proverbs 15:18, Proverbs 16:32, Proverbs 19:11, Proverbs 25:28, Proverbs 29:22). People of character do not let anger rule them (Proverbs 22:24-25, Ecclesiastes 7:9, Galatians 5:19-23, 1Timothy 2:8, James 1:19-20).
Anger has two brothers which Jonah shows us - selfishness and depression. When God called him to preach to the Ninevites because He wanted to give them a chance to repent, Jonah refused to go. He prayed for his own deliverance, but not for the Ninevites. He wanted to see them destroyed. He also did not care about his shipmates and the danger he put them in. He cycled quickly through two bouts of anger and depression because God spared Nineveh when they repented. He complained twice to God about his depression, but God responded by asking him if his anger was justified.
A great key to managing anger is forgiveness. If we were as quick to forgive as we are to get angry, the world would be a much better place. Forgiveness is not optional. If we want God to forgive us, He requires that we forgive others (Matthew 6:14-15, Matthew 18:34-35). When we remember the cross of Christ, it should be hard to hold a grudge against our fellow man (Leviticus 19:18, James 5:9). Hebrews 12:5-17 talks about a root of bitterness that defiles us, and tells us to let it be healed. Let means permit. That means we control whether we are bitter or healed. This is not always easy, but it is always necessary. It may take time for the wound to heal, but we must not keep picking at the scab. How can we love God if we do not love His children (1Jn 4:20)? Anger and unforgiveness are a prison. Everyone involved is in it unless they choose otherwise. The offender cannot be released unless they repent, and the offended cannot unless they forgive. Forgiveness is just as much for the victim as it is for the offender.
Controlling anger is a process that must be learned. It starts with self-evaluation. What makes you angry? Pay attention to your own behavior and learn what your buttons are. We all have them. Honesty and humility are key to this process. Once you recognize your patterns, develop a strategy to find a better reaction. This does not come naturally. We have to deliberately work at it. It takes practice. God does not take something bad out of us without replacing it with something good. Praying, delaying our words, slowing down our breathing, and sometimes even walking away are techniques to keep us from sinning in anger. Memorize some of the above scriptures and say them instead of something hurtful you cannot retrieve. When we fail, we need to ask God and others for forgiveness, and keep working on it. As Ephesians 4:26 advises, settle the argument before the end of the day if at all possible. "Blessed are the peacemakers: for they shall be called the children of God (Matthew 5:9)." Do not give up. You can do it. If you are filled with the Holy Ghost, He will bear His fruit in and through us. If you are not, repent and receive His power.