The first category of persons is easy to refute — just talk to their family members; while the latter kind are contemptible, but such is the way of the world, the flesh, and the devil.
But for some of us there has to be a fourth category: sinners who know they are sinners but who apparently don't want to be saints, for they persist in sin. But the following Psalm contains clues towards a way out of this problem. Those who persist in sin are often crushed by God, but are not destroyed; instead we ought to pray for a clean heart and steadfast spirit.
This Psalm is of great importance, both liturgically and theologically; it is almost a poetical catechism of penitence.
The fourth penitential Psalm is by David, composed after the prophet Nathan confronted him with David's great sin, namely of sending a man to his death just so that he could have his wife. (see 2 Samuel 12)
Confession, prayer, and promise of a penitent sinner.
Psalm 51 (Septuagint numbering)
Have mercy on me, O God, according to Thy great mercy;
and according to the multitude of Thy tender mercies: blot out my iniquity.
Wash me from my iniquity; and cleanse me of my sin.
For I acknowledge my iniquity, and my sin is always before me.
Against Thee alone have I sinned and done evil in Thy sight; that Thou mayest be justified in Thy sentence and mayest overcome when judged.
For behold, I was conceived in sin, and in sin my mother conceived me;
For behold, Thou hast loved truth, and the uncertain and hidden things of Thy wisdom Thou hast shown me.
Thou shalt sprinkle me with hyssop, and I shall be cleansed, Thou shalt wash me, and I shall be made whiter than snow.
Thou shalt make me hear of joy and gladness, and the bones Thou hath crushed shall rejoice.
Turn away Thy face from my sins, and blot out all my iniquities.
Create in me a clean heart, O God, and renew a steadfast spirit within me.
Cast me not from Thy presence, and take not Thy holy spirit from me.
Restore unto me the joy of Thy salvation, and strengthen me with Thy spirit.
I will teach the unjust Thy ways, and the wicked shall be converted to Thee.
Deliver me from blood guilt, O God, the God of my salvation, and my tongue shall extol Thy justice.
Thou shalt open my lips, O Lord, and my mouth shall declare Thy praise.
For if Thou didst desire sacrifice, I would have indeed given it, with a burnt offering Thou art not pleased.I ought to note that the Psalm's references to the Old Testament animal sacrifices are a type and figure of the most perfect sacrifice of Christ on the Cross, re-presented at each Mass. During Mass, we also offer ourselves as a sacrifice along with Christ: but is this sacrifice pleasing if we lack a contrite heart?
A sacrifice to God is an afflicted spirit, a contrite and humbled heart, O God, Thou shalt not despise.
Deal favorably, O Lord, in Thy good will with Sion that the walls of Jerusalem may be built up.
Then shalt Thou accept the sacrifice of justice, oblations and whole burnt offerings, then shall they lay calves upon Thy altar.