A best friend breakup is the worst kind of breakup. You lose your compainion, your other half. It's hard, going through something like that, and it's worse than losing a boyfriend, because yes, though you and said boyfriend could've been the best of friends as well as dating, there's just a different type of bond you have with someone you see every day at school or work, someone you don't have that romantic intimacy with, that you can tell all your details too, but then all of a sudden they're just not in your life anymore.
You think about all of the good memories you had together and all of the bad, and you try to weigh in if it's really worth it to try again. Maybe it is, maybe you just needed a break from each other to grow. Or maybe it really is a forever goodbye. Either way, parting with a best friend is heartbreaking.
I recently had to stop talking to one of my best friends, right before moving away to college and going through sorority recruitment. It took a huge toll on me, emotionally and physically. I had lost one of the only people who could make me laugh until my sides were sore. Though we were having our difficulties, I would spend hours on end just wallowing over the fact that I would never get to reference a certain inside joke, or hear a certain song and not remember her. It was extremely difficult to disconnect certain places, songs, and even other people from her. And to this day I still think about her, and how she's doing. I don't wish her anything bad. In all honesty, I wish her the best that she can possibly get, because she was, at one point, my main supporter. She and I shared moments that are irreplaceable. Does that invalidate my newer friendships now? Of course not. Every relationship is different.
If you've recently, or ever really, lost a best friend, then this hits close to home. Nothing lasts forever, but you can sure hope. And you can always start again. I challenge you to reevaluate your situation, reach out, check up on someone. Even if it's just a quick hello, you have nothing to lose.