We have all had thoughts that God couldn't possibly forgive us of a certain type of sin. Especially if we have already been before Him and repented of that same sin. We tend to believe that God thinks the same way we do, in that, if someone sinned against us the way we sinned against God, we could never forgive them again and would always remember their offense. God is so full of mercy! What if He wasn't merciful? What if we had to pay the penalty for our sin immediately? Just one bad thought would strike us dead! He even lets us carry our sin around without repentance, like a badge. Then when the burden is too much for us to bear, we finally turn to Him for forgiveness. He doesn't turn us away, but welcomes us back and forgets our sin. Our Father has such compassion for us and wants to forgive us. Don't wallow in your sin too long, go to Him and He will forgive you.
"Seek the LORD while he may be found; call upon him while he is near; let the wicked forsake his way, and the unrighteous man his thoughts; let him return to the LORD, that he may have compassion on him, and to our God, for he will abundantly pardon. For my thoughts are not your thoughts, neither are your ways my ways, declares the LORD. Isaiah 55:6-8