Long story - you can skip to the bottom for a summary and feedback question.

So, there's is this guy that I used to have a HUGE crush on...we met through mutual friends, at one point I thought he was interested in me but things never jelled, we were friends and I was sad but OK, just happy to have a cute fun boy who was my friend in my life. Until, at some point, for particular reasons, things got weird and I distanced myself from him because his behavior to me had become frequently rude. At some point, I just gave up all together and have actively avoided him, this was not hard because I had a falling out with the main mutual friends. And basically, we have had no contact for over seven years? except for this one time where we were at the same music venue and he happened to see me and I couldn't hide. Eyeballs were stared into but no looks nor acknowledgements exchanged. Whatever.

The big issue is myself. Because of social media, that he is a social animal and we have a few random tenuous social connections, I have a good grneral idea of what he is up to...And I find my self seeking out those images, I can't seem to stop. I feel like I am 'over him' and have moved on and been interested in other men, but I can't seem to resist, say, checking his facebook profile once a week. Recently, I was looking at party pictures (of a party I did not go to) and you can basically see him picking up a girl. And because I 'know him', want to scream at him and warn that girl away. (I am not the only woman I know he has been jerky too and strung along, I know this!) WHY? Why should I care? I am sure the lovely young woman is an adult and can deal with his douchiness, because it will show up, and he's not the only person in the world to have met an attractive person at a party and hooked up/dated/etc... that is what is to be a human, amiright? And yet, when I look at these pictures and having been at similar parties with him and seen him do the same thing repeatedly...and knowing these other women rarely last...I want to warn her off. Why do I even care? I used to feel pretty smug sometimes like 'Oh, sure, he's picking up some girl in front of me but after he's done with her this weekend I'll still be the friend who gets to hang out with him'. And try to pretend I wasn't hurt when he walked out the door with whatever girl it was while giving me a smug look. Ugh. What a fucker. He's so handsome and charming and it's oh so easy for him...it makes me mad! Maybe that is what I am really jealous of? His ability to find a warm body for the night and not care if he hurts their feelings (maybe they won't care and I am projecting waaay to much)...while I struggle to make meaningful connection with a man and I always feel the pull of my attraction to him when I met someone new and compare...

TL; DR — What kind of therapy or actions would you suggest/have you done when you've had problems letting go mentally of someone in your past? I've avoided/ not contacted him for so long, so the issue of separating is not a problem, but sometimes old thoughts die hard.