old friendship

so I feel ridiculous even writing this post. but I need advice. my childhood best friend and I stopped talking probably 10 years or so ago. I have never gotten over it. I still miss her and wish I knew what happen. I think we just had different friend groups and she drifted apart. I can’t let it go. It still upsets me and I would do anything to try our friendship again, which probably wouldn’t even work out because the last time we were friends we were children. I feel so stupid that I am

So hung up on this and it’s been years. I doubt she’s even thought twice about me. Does anyone know how I can let go and find some closure?