Forgiving others who have sinned against you is a big part of following God. You need to make sure that you have forgiven them the same way that God forgives you for sinning. Here is a prayer you can use to ask God for the strength and grace to forgive others:
Dear God
(Name) has done something nasty to me and it’s very difficult for me to forgive them for it.
I’ve been trying and trying to forgive them but I keep remembering what they’ve done.
It hurts to think that they would do something like that to me.
Please help me to forgive them and put this behind us.
I want the relationship to go back to the way it was and I know forgiving them is the right thing to do.
But I need Your help to forgive this person because I can’t do it alone.
Amen