Several years ago, I asked God the same question myself after becoming quite angry with someone. The Lord spoke to my heart and said, “Joyce, anger is not a sin—it is what you do with it that becomes sin.”
Ephesians 4:26-27 (AMPC) says, When angry, do not sin; do not ever let your wrath (your exasperation, your fury or indignation) last until the sun goes down. Leave no [such] room or foothold for the devil [give no opportunity to him].
These verses don’t say, “Don’t get angry” or “If you ever get angry.” They say, “When [you are] angry.” We’re all going to be angry at times, but it’s not feeling anger that’s a problem. The problem comes when we act on those feelings.