For I acknowledge my transgressions: and my sin is ever before me.
I acknowledge my transgressions. Giving the ground on which his prayer (Psalms 51:1-2) rests-namely, "I acknowledge my transgressions." They who acknowledge their sin are in a receptive state for God's grace. So in the parallel psalm (Psalms 32:5). David had confessed his sin (2 Samuel 12:13; cf. Proverbs 28:13). Not that confession is the efficient cause of forgiveness: the grace of God, through the atoning blood of Christ, is the only meritorious cause.
And my sin is ever before me - I can never lose sight of it.