The Bible says in 1 Corinthians 10:12, Wherefore let Him that thinketh he standeth take heed lest he fall. Peter’s denial of the Lord is mentioned in all 4 gospels. He failed every test the Lord ever gave Him. Jude says He is able to keep us from falling. We fail the Lord when we do not lean all our weight upon Him. Though Peter failed every test yet he graduated the valedictorian of his class. He preached the valedictorian address at Pentecost and 3000 people were saved. That my friend is the height of grace and mercy.