Loosing a friend... it's a painful thing, one might try to get them back, but it results in only more sadness.

Never dwell on this lost, yes I understand it's painful, I understand it's heartbreaking.

But,

This is not the end of your story, it merely the end of their chapter in your life.

So if they finished their chapter, don't try to rewrite them back into your life, just let them go....

There are still many chapters left to write...