Be angry and do not sin; do not let the sun go down on your anger, and give no opportunity to the devil. Let the thief no longer steal, but rather let him labor, doing honest work with his own hands, so that he may have something to share with anyone in need. Let no corrupting talk come out of your mouths, but only such as is good for building up, as fits the occasion, that it may give grace to those who hear. Ephesians 4:26-29
I have learned from experience that conflict is inevitable, nobody likes it, but sooner or later you're going to have to deal with it and there is a proper way to do it. God says to "Be angry and do not sin." Kinda sounds like an oxymoron but it's not. Anger is a God given emotion that occurs when injustice happens. Even Jesus got angry when merchants used the temple for a marketplace instead of a place of worship.
Our problem is that we get angry for the wrong reasons, we let it get out of control and we don't deal with it right away. It's best to deal with the source of the conflict as soon as possible and then let it go. "Don't let the sun go down on your anger, and give no opportunity to the devil." When you hold a grudge you give the devil an opportunity to worsen the situation. God desires that we pursue peace with all men.
Know this, my beloved brothers: let every person be quick to hear, slow to speak, slow to anger; for the anger of man does not produce the righteousness of God. James 1:19-20
Scripture says that God is "slow to anger and quick to forgive" but many times we are quick to anger and slow to forgive. We need to learn to listen more and speak less when conflicts arise. "A truly wise person uses few words; a person with understanding is even-tempered." Proverbs 17:27
Many communication problems are listening problems. Too often we don't hear what the other person is saying because we're too busy formulating a response in our head.
Let your speech always be gracious, seasoned with salt, so that you may know how you ought to answer each person. Colossians 4:6
When grace saturates your speech it changes the content and the tone of what you say. Choose your words carefully, not just reacting and blurting out the first thing that comes to mind. Avoid being sarcastic and condescending because that only exacerbates the situation. Speak the truth in love.
And do not grieve the Holy Spirit of God, by whom you were sealed for the day of redemption.Let all bitterness and wrath and anger and clamor and slander be put away from you, along with all malice. Ephesians 4:31
Bitterness occurs when you hold a grudge and won't forgive. It's an inward hostility that poisons you from within. You want to hurt them but you only hurt yourself. "Bitterness is like drinking poison and waiting for the other person to die." Bitterness eats you up inside and what's worse is it grieves the Holy Spirit of God.
Be kind to one another, tenderhearted, forgiving one another, as God in Christ forgave you. Ephesians 4:32
When someone hurts you, it's only natural to want to hurt them back. You want to punish them. Forgiveness is sending away your right to punish. Don't confuse forgiveness with reconciliation. Reconciliation takes two people, forgiveness only takes one. Be willing to forgive whether the other person apologizes or not. The only alternative to forgiveness is bitterness. Forgiveness is costly. Jesus sacrificed His life on the cross so that we can be forgiven of our sins.
For if you forgive others their trespasses, your heavenly Father will also forgive you, but if you do not forgive others their trespasses, neither will your Father forgive your trespasses. Matthew 6:14-15