Sad about my Bestfriend leaving

So, I’ve been thinking about how my Bestfriend will be leaving for training next month on the 14th. Idk what I’ll do without her. I mean my other Bestfriend is already in the navy and we hardly talk but I miss her like crazy as well. But it’s like they are the main people I talk to and not having them here I’ll be so alone. It sucks but I’m proud of them. And I’m so damn happy they are making a career for themselves. Do you guys have any of these problems with your friends? How do you guys cope with it?