“Who can know all his errors? Please do not punish me for sins I am unaware of.”
Only God is omniscient. We cannot know ourselves thoroughly. We need his guidance and insight, vv. 7-11. It is important to be aware of what we are unaware of.
Our limited knowledge of ourselves calls for humility. The Christian can be sure that as he walks in the light, the blood of Christ cleanses from all sin.