Catechism of the Catholic Church §1810 — excerpt
Human virtues acquired by education, by deliberate acts and by a perseverance ever-renewed in repeated efforts are purified and elevated by divine grace. With God's help, they forge character and give facility in the practice of the good.
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.