This psalm of David reveals that those who walk with God and who live according to His commandments, still need God’s mercy, healing, and deliverance. The purpose of keeping commandments was never perfection so that mercy and grace would no longer be necessary. In fact, David says:
“Oh, save me for Your mercies’ sake!” Psa 6:4
Not for my righteousness’ sake, but for Your mercies’ sake, save us, Lord. I have not yet found the place in the Old Testament where it says that salvation could ever be anything other than an act of God’s mercy to those needing mercy.