Let they who have not sinned cast the first stone. Focusing on the past is neglecting the future.
When a crowd brought the woman taken in adultery before Jesus, demanding that she be stoned, as the law required, Jesus said "Let one who is without sin cast the first stone." Almost instantly, a stone flew over Jesus' head from behind and struck the woman, knocking her down. Jesus turned and said, "Y'know, Mom, sometimes you really piss me off."