It's the pits
Like a halftime show between awake and asleep stretched out forever, band still playing and cheerleaders still dancing at the faintest edges. Like a sequence of words you need to say that won't come out right, their every iteration looking less satisfactory than the last. Like staring through the window of a cosmopolitan restaurant in winter, the inside filled with warm colors, smells, and people as your breath forms condensation on the ice-cold pane. Each interpretation maddening if only because it's impossible to make out clearly, each subtly but tangibly reminding you of the blissful state that so recently went away.
Comedown is one of those sensations which, at the time, you never want to experience again. But by its nature it is easily forgettable, and invariably, you end up in the same place, coming down once more. In the first hours you wonder how long until the drug leaves your system, you estimate times and plan diversions. Soon you begin to wonder if you'll be whole when it does, or if you're irreparably damaged inside. Finally your reason mostly ceases, and you simply wonder if it will ever fucking stop.
Eventually you find sleep. Fitful at first, sleep so light that you don't feel it come and go, only getting more tired as the glowing red bars coalesce into different numbers. Later, you sleep the sleep of the dead, after which your girlfriend will ask why you didn't answer her calls and your boss will ask you why you missed your shift.
And later than that, by hours or by days or by months, you will do it all again.