I recently read a novel about a group of childhood friends coming back together after nearly 30 years apart.
One of the characters said this about the slide from adolescence to adulthood: The energy you drew on so extravagantly when you were a kid, the energy you thought would never exhaust itself - that slipped away somewhere between eighteen and twenty-four, to be replaced by something much duller... It was no big deal; it didn't go all at once, with a bang. And maybe that's the scary part. How you don't stop being a kid all at once, with a big explosive bang. The kid in you just leaked out, like the air out of a tire. And one day you looked in the mirror and there was a grownup looking back at you. You could go on wearing bluejeans, you could keep going to concerts, you could dye your hair, but that was a grownup's face in the mirror just the same. It all happened while you were asleep, maybe, like a visit from the Tooth Fairy.