Today is the feast of St. Teresa of Jesus (Avila).
One of my favorite quotes from St. Teresa is, "Prayer is the trap door out of sin."
So often people are told that if they are in a state of mortal sin they cannot merit any grace, and their prayers and good works are not efficacious.
Nevertheless, it is important that the sinner never give up prayer. Pray as best as he knows how, and as often as he can - even when he feels he cannot quit his sins. God never fails to hear prayer, especially the prayer to be free of ones sins, placing all of ones confidence in the mercy of God. We do not have to be perfect to pray. The idea of merit? Leave that to the Blood of Christ.
Pray, pray, pray without ceasing, this is how you will attain eternal life.
St. Teresa, teach us how to pray and obtain for us a greater thirst for prayer.