Why do memories of them still pop up, even though I don’t want them to

It’s been a few months my ex and I split apart, around August of 2024. We were long distance (1400 miles apart) and my first relationship with someone. Dumb choice for a first relationship? Maybe or maybe not but I was happy though the long distance took a toll. I came to realize I was an avoidant anxious person after the break up and realized my wrongs in the relationship. I never really realized it though until last year when things started to go stale and distant, nothing felt the same anymore, we wouldn’t call or talk as much, granted they had school and also got a job so I was happy for him, but for some reason it made me somewhat upset even though it wasn’t his fault for any of it, leading me to be avoidant and distant. So that slowly took a toll and it didn’t help that he also became friends with a coworker who got pretty close together. Then it started to get even worse and worse until we had an argument that really took matters far and at that moment he wanted to take a break for a few months. I respected it and I thought well this is the end of us but I just wanted to see what they wanted in the end during the break. However my anxious attachment made me stalk them on social media and couldn’t help myself, they made a playlist on spotfiy together, starting following each other on other social media (maybe I’m overreacting with all of this) and so forth. I was in the wrong and broke the silence and the break when I decided to speak up when I saw something in their Spotify playlist description saying “perfect couple” and had to confront him about it and he denied that was the description and it somehow changed to “best duo” when I looked back. He got upset that I was stalking and asked if I could stop doing that so I did. Then I asked my sister about the whole thing and she said a few months to think about our relationship while getting closer to another person is just unfair to me. I also came to realize that a few months to think about it did seem kind of a stretch so I decided to take the bullet and reach out to them about not needing the whole break. I thought things were going well, catching up with each other until I learned that his coworker started to live with each other due to some housing issues he had. What was even worse was that he told me they cuddled in the same bed together which made me very confused and upset and I finally realized “This relationship is already over they just won’t say anything about it or realize it” Maybe it’s different to some people, but I don’t think friends cuddle within knowing each other a few months or so. So I finally just said to make up their mind whether or not we were gonna work out or not and they finally said it didn’t feel the same anymore and we should end it. I felt both a sigh of relief and sadness, realizing there was no more tiptoeing around the subject and yet my person I thought I was gonna be with forever was no longer mine. So I tried to discuss with them how the break up was gonna go, to discuss boundaries and what not though it seemed like they didn’t wanna talk to me at all and just wanted it to be over with, granted I guess they don’t have to give me that time since we aren’t together anymore but it’d be nice to just at least have a few minutes to talk about it. We finally did in the end but I don’t think I got any closure from it nor do they owe me any. I said my goodbyes and everything, my appreciation and what I could’ve done better, wishing them the best in life and just started to delete everything of them, unfollowing them and what not, trying to get them away from my head. Avoiding him didn’t last long though when I realized that him and his coworker already got together a week or two after we broke up so I thought maybe I deserve this and it’s probably better that he had someone in person anyways rather than a long distant relationship. After seeing that I started to block them on everything as well to avoid any sort of recommendation of their account and I thought that’d help, which kinda did but up to now, I just can’t help but think of them sometimes or the memories we had together and I just want it to stop. I don’t think we should be together anymore and I’m glad he has someone but I’m stuck in my rut again of will I ever be loved like that again and all that. The only thing I was glad on was that we never hated each other in the end nor was the relationship toxic, we just grew apart. I just wanna know how to stop thinking about them and learn to heal, because I’d hate to go into another relationship with my ex still on my mind because that’s so unfair to the other person. I’m in no rush to get into another relationship as I’ve got plenty of time (21M) but I just want the thoughts to stop. They aren’t even constant they just come out of nowhere then the thoughts just flood after that single memory comes out. I even daydream about it at work sometimes. An example of one I have is they for some reason come to my work and I see them, and both greet them, meeting their partner for the first time, asking what their business was in my state yadda yadda, and just hitting off and just being happy seeing my ex be happy. I feel like I’ve moved on but the same time these thoughts haunt me so I just want them to stop and finally find peace. I don’t know if I’ve even accepted my feelings or not I just don’t feel anything anymore. It just feels unfair. Sorry if my ramble makes no sense or any grammar is confusing, I just needed to get this out there because I don’t really tell anyone about my ex unless they ask about it so I appreciate anyone that stops by and reads this. Thank you