For his unfailing love toward those who fear him is as great as the height of the heavens above the earth. He has removed our sins as far from us as the east is from the west. The Lord is like a father to his children, tender and compassionate to those who fear him. For he knows how weak we are; he remembers we are only dust.
The level of which you forgive others is the level you'll be able to accept God's forgiveness for yourself because that's the extend of which you perceive forgiveness to go. By limiting how much you forgive someone, you're limiting how much God is able to forgive you. You're limiting your peace of mind, because you think God forgives in the same fashion as you.
This is not so, the minute you're born again, you become a child of God and the bible says that as far as the east is from the west, so have the sins of His children been forgiven. He doesn't hold them against you anymore. He won't come back and say, remember that time you did xyz? Those thoughts are not from God, but from satan, the accuser. So when the Lord says He has forgiven you, know that He won't come back and hold it over you, so you shouldn't hold it over yourself either. And since we know this, we should also use this same method of forgiveness when forgiving others. Don't forget, the bible also says in matthew 6:14-15: “If you forgive those who sin against you, your heavenly Father will forgive you. But if you refuse to forgive others, your Father will not forgive your sins".
So when you go to ask God for forgiveness, be sure to also forgive those who have wronged you. Then rest in the truth that once God has forgiven you, you can move from glory to glory. Repent from it, and continue the good fight of endurance. Besides what do you have to lose other than the bitterness and resentment in your heart?
Then Peter came to him and asked, “Lord, how often should I forgive someone who sins against me? Seven times?” “No, not seven times,” Jesus replied, “but seventy times seven!