Realize that you can still keep in touch with him/her, and it's not the end of your friendship. Call, text, Facebook, Instagram.. There are tons of ways to keep in touch and to stay very good friends, while at the same time maybe start to hang out with new friends.
Think about something else. My best friend moved away a couple months ago. You could try to not think about it and try to make new friends but still keep in touch with text, calls, facebook or something else and try to meet up somewhere again