Go, Show Yourself to the Priest
The confession (or disclosure) of sins, even from a simply human point of view, frees us and facilitates our reconciliation with others. Through such an admission man looks squarely at the sins he is guilty of, takes responsibility for them, and thereby opens himself again to God and to the communion of the Church in order to make a new future possible.
Confession to a priest is an essential part of the sacrament of Penance: "All mortal sins of which penitents after a diligent self- examination are conscious must be recounted by them in confession, even if they are most secret and have been committed against the last two precepts of the Decalogue; for these sins sometimes wound the soul more grievously and are more dangerous than those which are committed openly."
When Christ's faithful strive to confess all the sins that they
can remember, they undoubtedly place all of them before
the divine mercy for pardon. But those who fail to do so and
knowingly withhold some, place nothing before the divine
goodness for remission through the mediation of the priest,
"for if the sick is too ashamed to show his wound to the
doctor, the medicine cannot heal what it does not know."
"Individual, integral confession and absolution remain the only ordinary way for the faithful to reconcile themselves with God and the Church, unless physical or moral impossibility excuses from this kind of confession." Here are profound reasons for this. Christ is at work in each of the sacraments. He personally addresses every sinner: "My son, your sins are forgiven." He is the physician tending each one of the sick who need him to cure them. He raises them up and reintegrates them into fraternal communion. Personal confession is thus the form most expressive of reconciliation with God and with the Church.
-- Catechism of the Catholic Church
paragraphs 1455, 1456, 1484
Then I acknowledged my sin to you,
my guilt I covered not.
I said, "I confess my faults to the LORD,
and you took away the guilt of my sin.
-- Psalm 32