Everyone's been there. Someone cuts in front of you. A co-worker does something mean. Someone insults you out of the blue. How should you respond?
The first instinct of course is to snap back at them. You want to assert your dominance over the situation. You want to "teach them a lesson", so they won't do that again. Let's be honest, does that ever work? At best they already know they made a mistake and are sorry. Alternately they will get angry back at you, and thus begins a cycle of increasing pain. You want to "pay them back", and then they feel they have to get you back worse, and it goes on. Not good.
"Vengeance is mine" says the Lord. In any case, it's not your job to teach them a lesson.
So what should we do here? What would help things? Take a giant step back. Realize that if they are lashing out, they are already hurting inside. The answer is clear.
You need to love them.
But, they just hurt you! How do you strive forward and do the right things while your own pain is healing? Refocus on God's grace. God's love for you. Realize that you have been forgiven for doing hurtful things. You must now extend that same forgiveness to them. Take yourself out of the equation and ask: what can I do to help them?
Showing love instead of hate will completely diffuse the situation. Let them know you care about them. You may even make a new friend.