Getting over people is both easy and difficult. Some people can affect you in ways you had no idea was possible and others are pretty much one tissue away from the memory wastebasket.
The ones you've really loved and I mean the ones you can both visibly see a future with are always the hardest to get over because you've had a future and now you need to rewrite your thoughts and plans. You never considered that you had to rewrite them. So your brain, your emotions and such do want to move on but you've got these plans in your head. Step one is the only step here: Realise those plans are never meant to be more than fiction, it's an alternate reality but not this reality. Let your alternate self be happy [that SOB] but your current self in this reality needs a new story.
I've been there ages ago. The first person I fell in love with [not my first relationship by any chance] and I parted in a strange way. We were both very much in love, but it was the wrong time. She wanted me in her life and I stayed till she started dating again at which point I asked for space, left and eventually landed in a longterm relationship. Once that relationship ended was when I realised holy fuck I was never over my previous ex (though I hadn't thought about her much) or rather relationship (because sometimes it's not the person but what you felt when you were in the relationship). Fortunately, since enough time had passed and I was older I had reflected on my life and realised well this isn't going to happen. We are acquaintances but I stay clear of her life. Mind you had she not told me explicitly when we broke up that she hoped that someday in the future we'd get back together the thought would never have crossed my mind.
[pro-tip: if you want someone you love to have lingering emotions over you - just tell them that someday in the future when we are better people and have matured maybe we can get back together. Of course, it makes you an asshole in ways]
To be truly over, you need to erase those plans, love yourself and then learn to love someone all over again [but mind you this will not be the same and try not to fall for the same type of person because it could set some unhealthy habits].
