Why is it that nothing seems to matter?

Okay so last night I saw the movie to save a life and it got me thinking about the way people act and react. I realized that for the most part nobody actually cares about half the people they know, let alone someone have never met. And for some reason the actions of one person never seem to matter. There is a girl I know and love who is going through horrible things in her life, unloving parents, an abusive father, suicidal friends, etc. And I have tried everything I can to make her feel better, all she does is reject me and likes me even less whenever I try. And if she hadn’t told me just to leave her alone I still would be trying. Why is it that after months of trying to help someone in desperate need of it there has been no positive effect on her!? There has only been a negative effect me. All I have ever wanted to do is help people who need it because no one has ever tried to help me but how can I make a difference if I can’t change one person’s outlook on life? I don’t want personal gain anymore or sympathy for my own problems, I couldn’t care less about myself right now! But I ask you now to think about this question, why is it that for some people they have given up so much that nothing seems to matter? That they still feel unloved even when someone pours their heart out to them? If you ever feel alone or want somebody to talk to then you can fun mail me =) and if you’re not depressed or lonely than try to cheer somebody up that is! One person may not be able to change the world but you can definitely improve somebody’s life!