Having grown up a military brat, I am constantly moving to new places and meeting new people. With each station, there comes a new house, a new school and a new group of friends. You spend your two or three designated years there making it home, before you inevitably have to pack it all up and do it all over again.
More often than not, you lose touch with those who had once been your best friends. Never purposefully, but you just get so busy with all the new things in your life that you don't realize you haven't talked to them or seen them in weeks, months and even years.
One of the great things about this lifestyle, though, is that you have friends in all sorts of places. And sometimes, out of the blue, they pop back into your life again, and it's like picking up right where you left off. After the initial nervousness and happy disbelief (yes, this IS happening), you catch up on what has been going on in each other's lives and reminisce about all the memories y'all made together. That person is the embodiment of a certain time in your life, and it's bliss to be transported back to it.
Moments and visits like these never last long enough, though, and before you know it, it's time to head your separate ways again. Yes, it sucks. Leaving never gets easier, but you realize just how lucky you are to have been given this opportunity. They will always be part of your life, and moving away isn't going to change that. And besides, you never know when the opportunity will come again to have another reunion.