Forgiveness has very little to do with the person you forgive, and everything to do about your relationship with God. Always remember that we are commanded to forgive (Mattitayu 6:14-15) and that forgiving someone demonstrates our love of God through our obedience.
Besides, forgiving is the only way to make the hurt stop.
No, really! If you know the pain of being sinned against, and feel the person that hurt you doesn’t deserve to be forgiven, then you have forgiveness all wrong. Someone hurt you once, but when you fail to forgive them you are just hurting yourself, over and over. Forgiving is how you stop the hurt, and (actually) has no effect at all on the person that hurt you. Most likely, that person doesn’t care if you forgive them or not.
Try to remind yourself that the other person, the one who hurt you, has to face God sooner or later, and nothing you do, including forgiving him or her, will change their relationship with God. The hurt they did to you was also a sin against God and they need to make that right with God; frankly, God doesn’t care if you forgive them or not, so far as their relationship with Him is concerned. He does care if you forgive them or not with regards to your relationship with God. So forgive, get past the pain and be more right with God. The blessing you receive for forgiving others is that the pain stops.
Now let’s cover another aspect of forgiveness: forgiving someone doesn’t mean you have to trust them, or let them back in your life, or even deal with them, ever again. Forgiveness is what we do to improve our relationship with God. If someone has stolen from you, and you forgive them, it doesn’t mean you have to let them know the combination to your safe. That isn’t forgiveness, that’s stupidity. Shaul (Paul) says that we shouldn’t do anything to provide a stumbling block that might cause someone to stumble (into sin) so if you know someone who is hurtful, don’t give them a chance to hurt you (or themself, for that matter.) If you know someone who drinks too much, don’t offer them a second round. If you know someone who is a gossip, don’t listen to them or share a secret with them. If you know someone who is lazy, don’t give them an important job to do.
You should forgive them when their sin affects you, but that doesn’t mean you have to give them the opportunity to continue to sin against you to “prove” you have forgiven them. Your forgiveness of others is between you and God, and no one else, and you don’t have to prove anything to anyone.
Consequently, when you sin against someone, you should ask them for their forgiveness. Before going to that person, confess your sin and ask God for forgiveness. After all, every sin we commit is, first and foremost, against God. David knew that and said so in Psalm 51, so ask forgiveness from God, then go to that person and ask forgiveness from him or her. And know that the rule works the same way: if they do not forgive you, it has nothing to do regarding your relationship with God. You sinned against someone and you asked for God’s forgiveness and for their forgiveness.Whether they forgive you or not is between them and God, and once you do what you know to be right (in God’s eyes) you should also forgive yourself and move on.
The saying, “To err is human; to forgive, divine” is more than just an old saw- it is an accurate definition of both terms. God says many times that we are to be holy because He is holy, and one way we can do that is to be forgiving. You don’t need to allow that person back in your life or to deal with them ever again, but you do need to forgive them. It doesn’t even matter if they know that you have forgiven them.
Just so long as God knows.