When do you let go....: Friend Edition

Something has really been weighing on my heart lately. When do you stop being a friend. I had a friend for so long preschool, elementary, middle, and almost through high school that I thought he would be my friend forever. But that didn’t work. We were always together when we were younger doing everything. Birthday parties, sleepovers, camping you name it. I was never the video game, and Boy Scout guy but I always had fun being around. I would build LEGO’s while they played XBOX.We never argued (maybe once or twice in middle, but anyways...) never fought so I am now confused as to what happened. I reflected on some crazy things that have happened but nothing major really that would break a friendship. After middle was the last year we were close as usually and things started to drift. My friend was in higher level course than I so, we didn’t see each other as much. But still were friends. I ran into him and his family once at a baseball game they seemed happy to see me. Talked a good game a lot even invited me to the house. But I didn’t feel comfortable going being that my “friend” didn’t invited me. In high school we started to talk less and our friend circle became totally different. Class that were not higher level were filled with CP who were on a path to nothing. I always excelled in school but never felt like I was on the level to go higher. I was comfortable with passing these easy classes even though I was told to advance. Anyway, our friendship started to strain there. Then in college it totally broke. We went almost two years without speaking to each other. I came home for a winter break and my mother asked me to help with a Christmas parade where his mother was present. Talking to her hearing her reflect on our childhood friendship made me think, where is my friend? That’s when I tried to reach out but was I too late. The conversations between us were always short, mediocre , somewhat unpleasant. But I never gave in. One of the longest conversations we had was when I asked for help in chemistry. He actually helped with a few problems. Felt like my friend was coming back. Even though our parents were close, and our brothers were in the same grade and school we never seen each other until our brothers graduation, which was also my birthday. Before the event a text was sent from me stating “are you coming to graduation” and “it’s my birthday don’t forget my gift” in a friendly manor. Of course he didn’t know what day was my birthday, I didn’t expect him too. I approached his father him having a big grin said, “ your gift is at the house”. I’m thinking you know dern well you don’t have a gift for me I’m not a naive little boy anymore it won’t work. After the service we talked for 2 mins then it was awkward and the event wasn’t about us reconnecting, but our brothers passing a milestone so I said my goodbye and left. I felt devastated all the way home. Foolish, why did I make a effort, I talked to my parents about it they said “why do you care so much, people grow older and change”, it’s not that simple. And now It’s Dec. 29 his birthday I still sent a message and I feel the same way as usually. Foolish, devastated when do I stop trying to be a friend to someone has obviously doesn’t want a friendship anymore. I low key want closure like what happened that made the friendship drift so far. I don’t even like people and avoid my friends on purpose to not be bothered but yet this one childhood friend, what happened. My question is when do I let go of it? Gemini says hi, lol.