"An oracle is within my heart concerning the sinfulness of the wicked: There is no fear of God before his eyes. For in his own eyes he flatters himself too much to detect or hate his sin." (Psalm 36:1-2 )
We don't get sin rightly. We don't see it like God sees it. We don't grieve over it like God grieves over it. To some degree, yes the Christian has had their eyes opened to sin or he/she wouldn't be a Christian. Yet our sinful nature still clouds in our heart the tragic realities about sin.
When we say, think, do, imagine anything that is not in perfect conformity to the law and mind of God, we sin. This grave moral disease includes doing things that we ought not to do, as well as leaving undone things we ought to do. We flatter our moral egos by comparing ourselves with others who sin more than us or don't do as much "good stuff" as us, instead of comparing ourselves to the character and law of God. When this right comparison is made, we can't help but run to Christ and treasure the gospel more deeply.
Let us pray like the psalmist: "Who can discern his errors? Forgive my hidden faults." Psalm 19:12 and let us treasure the one who knew no sin, but was made sin for us, so that in Him we might become the righteousness of God (2 Corinthians 5:21).