He knows that he wasn't the man he should have been when he was with her in the past and that the mistakes cost him what he had.
And he wants her back and to do so, he knows he has to be a better person, a better man and be better in relationships.
Additionally and interestingly, parts of the song suggest that he knows he has to be a better person within relationships and love with anyone and not necessarily his previous flame.
Quite a simple premise.
He knows that he wasn't the man he should have been when he was with her in the past and that the mistakes cost him what he had.
And he wants her back and to do so, he knows he has to be a better person, a better man and be better in relationships.
Additionally and interestingly, parts of the song suggest that he knows he has to be a better person within relationships and love with anyone and not necessarily his previous flame.