Being best friends with someone doesn’t mean that you Skype twice a week at a specific time every time. It doesn’t mean that you text each other all the time, or call every Sunday night before you go to sleep. You don’t have to litter their Timelines or their Ask Boxes with inside jokes or half-hearted “I love you”s in an attempt to keep the relationship as strong as it used to be.
Because if you really are best friends, you shouldn’t have to do any of that stuff to still be best friends. And you shouldn’t be upset if your counterpart in this relationship doesn’t do those things - people have lives beyond one friendship, and real best friends realize and respect that. Being best friends shouldn’t be work. It shouldn’t be hard. You shouldn’t feel threatened that the relationship is going to break just because your contact is somewhat lacking.
Being best friends with someone means that even when you’re apart for months, or sometimes even years, and you don’t keep up constant contact, and you both get other friends, and interests, and your personalities change, you still come back together at some point and you act like nothing has changed. Because nothing has. You’re still best friends. And if you feel like you need to prove that to each other, then you obviously never were.