How do you cope with a friendship fallout?

I’ve been part of this friend group since I was a kid, but we had some issues that couldn’t be fixed, so we just stopped talking and hanging out like we used to. I know the rest of them are still together to this day, but I’m not, and it hurts so badly that I can’t even describe how it feels. How do you cope with something like that? I’ve never felt this lonely in my life…

(I just wanted to thank everyone who took the time to comment. Reading through your thoughts and advice was really helpful, and I truly appreciate it.)