He denied the Lord. Jesus told him. When thou art converted strengthen the brethren. Convert means change to another option. For Peter go back to Jesus the one he was following. The Bible says when the roster or cock crowed twice he remembered the Words of Jesus and went out and wept bitterly. Or he repented. I think we all do something sometimes that we need to repent over. If not repented over. It could mean us going completely away from God. Especially if we keep doing it over and over again.