Rant #3: Is it normal to care this much about a drug addict and your used-to-be best friend?

Why?

Why do I care so much about the guy who lied to me and hurt me? Why does it kill me that he does meth, heroin, and pot? Why does it bother me so much that he drinks so much? Why did it kill me to see him with a cigarette to his lips? Why do I care so much about him, even though he's hurt me, even though I probably don't mean very much to him? Why do I still worry about him, still worry about all the stupid choices he makes? Why do I worry that he'll be in another drunk car accident...only this time, he won't survive it?

Why do I care about the guy who used to be my best friend, but now pretty much ignores me and doesn't care about me at all? Why do I miss him, and miss being around him? Why does it hurt so much when I know that he's in pain? Why does understanding that some things in his life are rough have to make me feel so bad for him? Why do I still care so much about him, even though he doesn't miss me at all?

Why do I still care and worry so much about these two people, when both of them have lied to me and hurt me?

Why?