Forgiveness truly is battling in the Spirit against satan and his demons. When someone holds a critical judgement against someone else, they are, in fact, coming into agreement with what the devil says about the other person and who they are. When they agree with what the enemy says, they actually free him to carry out his plan to completely destroy the relationship. Remember: the Word of God says satan comes to kill, steal, and destroy.
When you forgive the person who hurt you then you are coming out of agreement with what the devil says about the offender, and you come into agreement with what God says about them. In doing so, you free the Lord's Hands to fight on your behalf against the accusations of the devil. You also give the Lord "permission" by the act of your free will in agreeing with Him, to carry out His plan to bring restoration, peace and wholeness to your relationship. You literally chose a mountain top experience with the Lord rather than the low lying dark valley of the enemy.
The enemy will bring the offense up to you over and over to try and get you to side with him. This is when you forgive the offender 70 x 7. You must choose to follow the Lord's instruction to "having done all, to stand" in Ephesians 6 concerning spiritual warfare if you want to remain victorious. You have to stand firmly on your position with the Lord on this matter.
Next time someone offends you, ask yourself if you want to side with the Lord on the mountain top where the light shines brightest and agree with what He says about the person, or join the dark ranks of the enemy and agree with the accuser. Ask yourself, whose plan do you want to facilitate - the enemy's or the Lord's?
Choose peace. Choose forgiveness. Choose life in the Spirit of God. Choose unconditional love. Think the best and believe in the best about others.