Is it a sin to not truly forgive someone for something bad that they have done to you? Meaning hurt me in such a way that I just cant forget but I have told them that I forgive them but in my heart I have not, and it eats me inside everyday. I forgive but I really canít forget. Itís very hard.
I donít know that it can truly be called a sin not to forgive. I do know that it has a consequence that may make it have the same result as a sin. ďBut if ye forgive not men their trespasses, neither will your Father forgive your trespasses.Ē (Matthew 6:15) If you donít forgive, you canít expect forgiveness from God.
One other aspect of what you have said, that may make it a sin, is that you have told the person you forgave. Does that mean that you have lied about forgiving?
The other issue you bring up is forgiving and forgetting. While God may have the ability not to recall something he has forgiven, we humans canít always do that. However, remembering a wrong does not necessarily mean we have not forgiven it. Forgiveness is an action, not just in the mind. Forgiveness says we will not let our actions in regard to another person be colored by their actions against us. If we remember something they did that we have forgiven, we may have to make the effort to ensure that doesnít affect our actions. The degree to which we react negatively as a result of that memory is the degree to which we have not forgiven. There is no scripture that directly supports this idea, but it is based on the idea that love is an action and not a feeling. Feelings happen. What we do with them is what God is concerned about.