The people in RCIA are learning about sin and morality as they get ready to make their first confession. The general subject of sexual sin is always a challenge.
We are most uncomfortable with these sins of lust and gluttony when they are in many cases the secondary sons rooted in our selfishness and pride. Somehow we are lured into shame over these lesser sins by the greater sin of pride that blocks us from admitting what we are: sinners in need of a savior.
Paul reminds the Thessalonians (2 Thess 3:13) You must never grow weary of doing what is right, brothers. So we are reminded that the Christian life is for those whose strength is rooted in their honest admission of their weakness.
God knows what we did. His gift to us in the Sacrament of Reconciliation is both the absolution given through the priest and the insistence that we not take ourselves so seriously we cannot admit what we did.