Psalm 51:10-12 Create in me a clean heart, O God; and renew a right spirit within me. (11) Cast me not away from thy presence and take not thy holy spirit from me. (12) Restore unto me the joy of thy salvation and uphold me with thy free spirit.
This Psalm is a result of King David's sin with Bathsheba. He committed adultary, and in an effort to cover it up, he committed murder.
Satan delights in leading Christians into a backslidden condition. Then he convinces them they can't go back. He's a liar.
David knew that even with all his sin, God still loved him. For great sin there is great grace (Rom. 5:20).
Whether you think your sin is small or great, it breaks fellowship with God. No matter what you do, He still loves you and wants you to confess your sin. He will cleanse you, remove a mountain of guilt, and restore the joy of your salvation and sweet fellowship. He's been there all the time, waiting for you to return.