for then he would have had to suffer repeatedly since the foundation of the world. But as it is, he has appeared once for all at the end of the ages to put away sin by the sacrifice of himself. (Hebrews 9:26)
When you have been forgiven of all your sins by Christ you are completely forgiven. You have no need to forgive yourself.
Believing that you have to forgive yourself is nothing but unbelief. Simple, plain, non-excusable. Christ has done away with all your sin. it is done, over, finished! There is nothing left for you to do but believe it. Every evil action you have done, every person you have left destroyed, every heart you have broken is under the blood of the lamb slained! Don’t try to forgive yourself. You can’t! Instead, believe in the pronouncement made by the sovereign judge of the universe, “Forgiven because of Christ!”