"Pray constantly . . . Always and for everything giving thanks in the name of our Lord Jesus Christ to God the Father." St. Paul adds, "Pray at all times in the Spirit, with all prayer and supplication. To that end keep alert with all perseverance making supplication for all the saints." For "we have not been commanded to work, to keep watch and to fast constantly, but it has been laid down that we are to pray without ceasing." This tireless fervor can come only from love. Against our dullness and laziness, the battle of prayer is that of humble, trusting, and persevering love. This love opens our hearts to three enlightening and life-giving facts of faith about prayer.
Source: Catechism of the Catholic Church (Vatican.va)