<human>: So I've started dating this girl who's parents divorced when she was in her early 20's. She then dropped out of school and went through a period of drug use and shitty relationship to shitty relationship. 

She's now a very responsible person who has a good job and is making great strides towards her life goals.

I've had my own fair share of shitty experiences as well as friends who've had drug problems that have become well adjusted normal people. But for some reason whenever I hear stories about like this it just really bums me out. Our interactions are great, and she's hilarious and happy, but when I'm alone and think about her, I just can't help but imagine her being listless.

My reaction to this has been to treat it like it's none of my fucking business and I should be with the person she is now and forget about all the other shit. 

But this isn't the first girl I've had this sort of depressed feeling about their past, and I wonder why I do this to myself. Also, for reference, I can't watch the Bret Easton Ellis movie 'The Rules of Attraction' due to the early scene where the girl gets raped. I know it's fiction, but it's just too fucked up for me.

Could you distill the essence of the text into 1-3 sentences?
<bot>: New girlfriend had some rough patches, How do I learn to just not give a fuck and not feel sorry for her.