How do I move on?

A year ago, I was in a relationship with someone for a couple of months. We broke up over a misunderstanding. But I really felt a connection to that person and we shared a tremendous lot of memories together. It's almost been a year since we broke up and it feels like I can't really have similar feelings about anyone else anymore. I tried to clear the misunderstanding several times throughout this year and I put in a lot of effort into making amends but it seems like all of it went to vain. I swallowed my pride and ego and kept chasing that person despite the fact that the fact that my ex paid no heed to my efforts. It really hurt me from within how a person who you could be so close to could choose to ignore and disregard your feelings. I feel lost and I lack that sense of familiarity and calmness I felt with that person. Everything feels alright throughout my day but it gets really bad at night when I can't help thinking about it. I constantly check that person's social media. I've been blocked everywhere and I check my ex's social media through a fake account. I don't mean any harm but it just hurts me how someone can be just alright and going about their life like nothing ever existed.