I think its about a girl who lives her life for the praise she gets from others and shes been doing it for so long that its the only thing that gives her life anymore. He also mentions this type of girl someone who finds their identity in the approval of others is the type of girl that everyone writes songs about and these songs only feed her condition. And in his opinion someone who lives their life that way will grow a cold heart maybe because they see people as a means to an end always instead of thinking what they can do for them. And i don't think they do it on purpose i just think they believe that's all their capable of so they dont feel strong or capable to give anyone anything cuz they're constantly worrying about themselves because living your lifes for others praise builds only a fragile backbone onto your body that you always have to worry about whether its gonna break or not.
