This is "The Sweeper of Dreams" by Neil Gaiman from the book Smoke and Mirrors.
After all the dreaming is over, after you wake, and leave the world of madness and glory for the mundane day-lit daily grind, through the wreckage of your abandoned fancies walks the sweeper of dreams.
Who knows what he was when he was alive? Or if, for that matter, he ever was alive. He certainly will not answer your questions. The sweeper talks little, in his gruff gray voice, and when he does speak it is mostly about the weather and the prospects, victories and defeats of certain sports teams. He despises everyone who is not him.
Just as you wake he comes to you, and he sweeps up kingdoms and castles, and angels and owls, mountains and oceans.He sweeps up the lust and the love and the lovers, the sages who are not butterflies, the flowers of meat, the running of the deer and the sinking of the Lusitania. He sweeps up everything you left behind in your dreams, the life you wore, the eyes through which you gazed, the examination paper you were never able to find. One by one he sweeps them away: the sharp-toothed woman who sank her teeth into your face; the nuns in the woods; the dead arm that broke through the tepid water of the bath; the scarlet worms that crawled in your chest when you opened your shirt.
He will sweep it up – everything you left behind when you woke. And then he will burn it, to leave the stage fresh for your dreams tomorrow.
Treat him well, if you see him. Be polite with him. Ask him no questions. Applaud his teams' victories, commiserate with him over their losses, agree with him about the weather. Give him the respect he feels is his due.
For there are people he no longer visits, the sweeper of dreams, with his hand-rolled cigarettes and his dragon tattoo.
You've seen them. They have mouths that twitch, and eyes that stare, and they babble and the mewl and they whimper. Some of them walk the cities in ragged clothes, their belongings under their arms. Others of their number are locked in the dark, in places where they can no longer harm themselves or others. They are not mad, or rather, the loss of their sanity is the lesser of their problems. It is worse than madness. They will tell you, if you let them: they are the ones who live, each day, in the wreckage of their dreams. And if the sweeper of dreams leaves you, he will never come back.