This happens to everyone in life at some stage or another and there are really only a few options.
You can accept it for what it is or you can accept a broken friendship and try and move on but either way it’ll never be the same as it used to be.
Losing friends is hard, especially with people you have amazing memories with but people develop different interests, fall out, or simply grow apart and that, unfortunately is a part of growing up. However one thing is for certain, you will always make more friends.
Sometimes it’s just not worth the investment in trying to rebuild a broken relationship as there will always be underlying cracks.
What you realise in time is, that not everyone you lose is a loss.