First and foremost, this practice is not found anywhere in the Bible... and secondly, God forgave all sin back at the cross. There is no sin that remains to be forgiven of!
2 Corinthians 5:18-19
All this is from God, who reconciled us to himself through Christ and gave us the ministry of reconciliation: that God was reconciling the world to himself in Christ, NOT counting men's sins against them. And he has committed to us the message of reconciliation.
If God hasn't been counting sin against anyone for the past 2,000 years, why does the church system often use fear and condemn people for their supposed sins?
As this verse and others clearly say, God reconciled the world to Himself through Christ 2,000 years ago and believers should simply proclaim this Good News to unbelievers - the ministry of reconciliation.
It is by God grace and His Spirit that we are enabled to believe and even more so, to love God... fear and condemnation may cause people to "accept Jesus" as a "fire insurance policy", but rarely, if ever does fear and condemnation ever lead a person to love God.