Catechism of the Catholic Church §1732 — excerpt
As long as freedom has not bound itself definitively to its ultimate good which is God, there is the possibility of choosing between good and evil, and thus of growing in perfection or of failing and sinning.
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.