Catechism of the Catholic Church §2752 — excerpt
Prayer presupposes an effort, a fight against ourselves and the wiles of the Tempter. the battle of prayer is inseparable from the necessary "spiritual battle" to act habitually according to the Spirit of Christ: we pray as we live, because we live as we pray.
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.