I feel as though the song was about a person who got hook on drugs or alcohol and has tried to get off of them but the drugs keep talking to them (via their head) and trying to convince them to come back or not go at all. They (drugs) have a very strong hold on them and calls itself Kryptonite because it makes them so weak it's almost impossible to break away without help (Like Superman has to have every time kryptonite has him down someone comes to help him) and is fighting to stay alive in the person. It is made to sound like something all can relate to though a super unhealthy relationship and is really trying not to blame anyone but still at the same time is trying to deal with the guilt of the other person getting hooked (on the relationship)and blaming them and the first person wants to be friends no matter what. But the relationship is the addiction now and therefor the Kryptonite. Because every time they get together they get weak. That's my story and I'm sticking to it. Scott S.