Catechism of the Catholic Church §1847 — excerpt
"God created us without us: but he did not will to save us without us." To receive his mercy, we must admit our faults. "If we say we have no sin, we deceive ourselves, and the truth is not in us.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Whole chapters cited: 1 John 8 · 1 John 9
Also cites: St. Augustine, Sermo 169, 11, 13: PL 38, 923