A conversion is always a miracle itself. There are many people who have led wrong lives, and then changed their ways through grace, and who have became faithful and strong believers.
A prayer from the Divine Mercy, Jesus Christ:
“If you say this prayer, with a contrite heart and with faith, on behalf of some sinner I will give that soul the grace of conversion”.
O Blood and water that gushed forth from the heart of Jesus, as a fount of mercy for us, I trust in You.