Restore to me the joy of Your salvation, and sustain me with a willing spirit. — Psalm 51:12

David doesn't ask for a second salvation — he asks for the joy of it to be restored. The salvation itself is secure, but you can lose the felt sense of it when sin creeps in. I will heal your backsliding, I will love you freely. Come now, and let us reason together, says the Lord: though your sins be as scarlet, they shall be as white as snow. Bless the Lord, O my soul, who forgives all your iniquities and heals all your diseases.