I think this song is about depending on someone so much that you can't live without them. When you are with this person, you are not your single self anymore, you are not complete. You need this person to be complete otherwise you are nothing- you can't function, you can't exist.
I think this song is about depending on someone so much that you can't live without them. When you are with this person, you are not your single self anymore, you are not complete. You need this person to be complete otherwise you are nothing- you can't function, you can't exist.