I can fall asleep almost anywhere. I routinely fall asleep in the break room at work. Once, I was helping a friend fix his car, and I fell asleep on his garage floor when he went inside to get water.
But in a hot metal tube tearing through the sky, with my neck all kinked? Get out of here, man.
You may (or may not) be surprised to learn that modern jet liners have much higher glide ratios than small planes (like a Cessna 172), though even the glide ratio of a Cessna is pretty damn good at about 9:1, getting 9,000 feet horizontally for every 1,000 feet of altitude.
All pilots are trained in engine-out procedures as part of their license training and, while unequivocally an emergency condition, is fairly benign until it’s time to land—preferably on a suitable landing surface.
Face your fear and go on a discovery flight with a flight instructor at your local municipal airport.