Catechism of the Catholic Church §2725 — excerpt
Prayer is both a gift of grace and a determined response on our part. It always presupposes effort. the great figures of prayer of the Old Covenant before Christ, as well as the Mother of God, the saints, and he himself, all teach us this: prayer is a battle.
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.