I read this on Family Life yesterday. May it encourage you to never give up praying for your children, no matter where they are spiritually.
One of the greatest examples of [praying and trusting God with a rebellious child] is Monica, the mother of Saint Augustine. She watched him spend his teenage and young adult years rejecting her Christian faith while outdoing his friends in seeking sinful pleasures.
At one point she persuaded him to meet with an unnamed bishop from North Africa. The bishop refused to speak to Augustine because he considered him as yet unteachable. Even though the meeting proved unsuccessful, the bishop comforted Monica in her distress, saying, “It is impossible that the son of so many tears should perish” (from Confessions, St. Augustine).
You may well know the rest of the story: The Lord God dramatically converted Augustine in his Roman garden, urging him to “take and read” the words of the Scriptures that would open his eyes to the wickedness of sin and the promises of Christ. Only the mother of a prodigal can quite understand the joy in Monica’s heart when she held her now-grown son in her arms, rescued by God’s grace and a mother’s prayerful tears. She died nine days later — her purpose in living fulfilled. And Augustine went on to become one of the most influential figures in Church history.