I think this song is about a girl who has come from a family with problems to the point of her parents getting divorced. She never wants to see that happen to her because she saw how her dad reacted. So she has got it in her head that love doesn't exist and she doesn't want anything to do with the thought of love. Soon enough she find a guy who she really likes and she doesn't want to admit that she loves him so he tells herself that he is the "only exception" for her. Eventually she realizes that love is a real think and she is on her way to believing.