There's lots of good descriptors and comments in the notes, but one thing I'm not seeing is that at that level of exhaustion, your perception of time distorts. When you're microsleeping--between sentences, while you're walking, in the middle of performing other tasks--time can seem to be passing either incredibly slowly or incredibly quickly, as your brain cycles in and out of sleep in a fraction of a second. Your vision occasionally blacks out, but you also get darkness creeping in on the edges of your vision, crawling frond-like and narrowing the world to a dark tunnel. It's kinda cool! Your hearing is usually more reliable than your vision--you can listen and pay attention but keeping your eyes open is hard.
Decision making and focus also deteriorate. After five days of no sleep, punching myself in the throat in order to restore my lost voice seemed perfectly reasonable (and, for what it's worth, did work.) You can physically still accomplish strenuous tasks--I could still carry 100+ lb loads without significantly more strain than normal--but maintaining focus on the tasks is harder. Your body wants to relax and sleep, so to carry a heavy load, you have to actively force yourself to maintain your grip. Doing things like counting large quantities is near impossible, because you repeatedly loose focus and second-guess what you've done already. You stagger and stumble as you walk, if microsleep is setting in strongly enough to catch you as you're walking.
I hope you can benefit from my poor decision making. I may not be a role model but if nothing else I can teach by bad example.
