Reconnecting. There's nothing more eye opening than reconnecting with someone after a few months or years and realizing how much you've changed or how much the person's changed.
You kind of expect them to be the same or at least a little piece of you expects that. Depending on how the connection ended in the first place you may wish and hope the person has changed.
Initially it's awkward, whatever groove you had developed before is never the same. In a weird way you'll grieve the loss of that. This part of you and them has died and you'll miss it, you'll be sad. You may never recover that groove you may no longer be as close friends as you were before or the opposite e may be true. Your bond may be stronger than it ever was before.
I've always argued that friendships and romantic relationships have the same tenets, the same issues, take the same amount of work and can cause irrevocable damage if the end or get broken. My friends have been my family in the absence of such in my life and those relationships have been some of the most rewarding, most painful, most amazing experiences of my life.
We've grown apart, we've grown together, we're growing up.