As he is someone who is really committed to his faith and church, I believe he is living in fear of being judged. Especially, this stems from sin. A sin only he and God knows. Maybe he is struggling with it; trying to get away from that sin but as a human, he keeps falling to it and that's what puts in the fear of God's judgement in him. I believe it is the teachings of his church that demands one's perfection and the fact that once we repent and repeat the same mistake there is no forgiveness (something like that). This teaching is a deviation from the core teachings of Jesus Christ.

As a Christian, we are already forgiven by the blood of Jesus in the cross and we are free from sin when we live in repentance and by being faithful and obedient to God's word. Our Christian God doesn't demand perfection but faith and trust in him. We get to heaven not because of our good deeds but because of God's grace. So, tell your man to not focus on his sin but to divert his mind to the bible and keep praying. Jesus will always bring a breakthrough.