I've never felt such relief. Laying my head on the pillow, bracing myself for a full, guiltless sleep. Bliss. My polyphasic sleep experiment had ended. I could enter back into normal society as a fully rested, fully functional human being. At that precise moment my mind was empty, scattered, exhausted. Only later, after 13 hours of sleep, did I attempt take stock and ask myself: what went wrong? What could I have done better? Was my experiment a complete and utter failure?

"This isn't for you. You're not good at this," says my wife, shouting from the other side of the apartment. She's curled up in bed, reading a book, lazily. I'm hunched over the computer desk, jaw clenched, inches from a monitor screen. I can feel the pulsing of the brain inside my skull. "You're not Superman," she says. "You're a sleepy man."

Sleep deprivation -- it's like a barrier that shields you from the world. It's like trying to walk underwater, or pounding on the windows of a glass case. When you've had no sleep you evacuate your body, and keep the world at a distance.

The above video was made at roughly 4am. At that precise moment, I had never been more tired in my life. It's not in shot, but to my right is a television. I can't be 100 per cent sure, but it was most likely showing the Max Payne 3 kill screen. On it a single question: Retry/Quit?

The train has become my sworn enemy.

Mark's attempts to adopt the Uberman schedule of polyphasic sleep have already pushed him to the brink. Here's a video diary he filmed this morning at 3am. Surprisingly, he was in a better frame of mind than the night before, or when he write this morning's post. Can anyone say mood swings?

I was aware of it in the beginning, but somehow I forgot. I was aware the night before my last eight-hour sleep, when I curled up beneath my sheets. At that point I remember specifically thinking to myself: "tomorrow you can't do this". Or the night after that. Or the night after that.