Psalm 51:10-12 says 'Create in me a clean heart, O God, and renew a steadfast spirit within me. Do not cast me away from Your presence, and do not take Your Holy Spirit from me. Restore to me the joy of Your salvation, and uphold me with Your generous Spirit.' David was really crying out to God not to cast him away after the sin he had committed with Bathsheba and the murder of Uriah. His heart had known the mercy of God before while he had been running for his life during Saul's time as king, and David wanted fellowship restored with God. Nathan told David that God would forgive him, but the sword would not depart from his house (2 Samuel 12:10). After David's confession, Nathan said, "The Lord also has put away your sin" (2 Samuel 12:13). The Lord had forgiven David and it was gone - instantly. God will forgive us and never bring it up again, but we must be willing to admit our sins and ask Jesus for forgiveness. 1 John 1:9 says 'If we confess our sins, He is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.' God is faithful! Even when we are not faithful to God, He remains faithful to us. He loves us more than we can fathom and will forgive our sins completely and cleanse us. What an awesome God we serve! Romans 5:8-9 says 'But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us. Much more then, having now been justified by His blood, we shall be saved from wrath through Him.' It's because of the blood of Jesus Christ that we can be forgiven and washed clean from all unrighteousness. It's because of the blood of Jesus Christ that we can come to the throne of grace and obtain mercy, and find grace to help in time of need (Hebrews 4:16). God will forgive you. All you need to do is ask.