A gentle answer turns away wrath, but a harsh word stirs up anger. - Proverbs 15:1
Forgiveness isn't optional.
If your brother sins against you, go and tell him his fault, between you and him alone. If he listens to you, you have gained your brother. - Matthew 18:15
The beginning of strife is like letting out water, so quit before the quarrel breaks out. - Proverbs 17:14