‘Now therefore make confession unto the Lord God of your fathers, and do his pleasure.’ It’s a beautiful way of expressing it.
In our confession of any sin we recognise, as David does in Psalm 51, that our conduct, whatever it might have been, has brought shame to the cause and is grievous to God. It has grieved the Lord. It has grieved the Spirit within. It's a grievous thing that I've done, and I should be seeking to please him as one who is saved by him and given so much.