Anger is a natural emotion, triggered by abuse and injustice. We encounter hurtful people and injustices daily, and if we don't learn to let go of anger, we will be perpetually angry.
Therefore each of you must put off falsehood and speak truthfully to his neighbor, for we are members of one another. “Be angry, yet do not sin.” Do not let the sun set upon your anger..." (Ephesians 4:25, 26)