well she said that the song "is about being with someone you love, and you have to say goodbye, and all the little things you miss about them". The song could also have been inspired por her husband Deryck Whibley. Avril didnt intend it to be a amor song but she was composição literária it as a slow song so it brought out all of the emotion:)
The song was written about her ex husband, Deryck Whibley. Who was her actual husband at the time the song was written. So when Deryck went away somewhere for a bit then Avril missed him and wrote a song about it.
