The song talks about a man who most likely was an a$$. He met one of those one in a million girls that would love a man like him no matter what. A person who cant hate and doesnt have the heart to leave some one alone. He might have put her through hell, but shes still with him. SO hes saying that she should leave him because he knows she'll get hurt, but she wont. And there isnt he can do to make her move on.