Like most people, around 3 o'clock in the afternoon on every week day, I start to feel drowsy. If I'm unlucky I actually close my eyes and my head jerks about and I am startled awake.
To stay awake I have to monitor my caffeine intake (not very well sometimes). I have tea in the morning to keep me going to lunch then after I have eaten I'm usually a bit more aware of everything for a few hours. Then comes the pro plus tablets to keep me going just a little bit, then by 4, my thermos is my best friend. Coffee at the ready, I manage to stay awake long enough to make it to the end of the day.
As soon as I step outside the cold wakes me up, but as soon as I'm on a train I'm alseep. Today it was a deep sleep, I almost missed my stop.
Of course this fragile routine is disrupted depending on the environment I'm in. Most people fall asleep if they are warm and stay alert if cold. I am the opposite. I have the strange ability to fall asleep at will. If I had super powers, sleep would be it, if you could weaponize sleep. If the temperature of the room drops, that's it, game over, I can't fight it (which is why I can fall asleep on trains with ease). If I am at work and the weather changes in the rooms, which it always does if we have to move, I find its battle of the radiator. The majority want the heating off to stay awake while collapse and my head bobs up and down as I remember where I am.
If there ever comes a time where I'm in a warm room and everyone is half asleep, except me, and there was some kind of apocalyptic emergency, I would be humanities' last fully awake hope (in this scenario only). I would have to fight sleep off in various tasks. I would beat sleep and named a victor! But of course out of everyone, I'd probably would be sitting in my desk chair next to my bed face down on the bed, fast asleep, as my Uni house mates used to find me sometimes. That's where I would be while the real heroes solved the obscure problem.
Being able to sleep any where, anytime is curse as well as a gift of sorts. When I was still at school I would walk in the front door, sit on the hallway floor in an awkward position and literally fall asleep for a few hours. My mum would come in and say 'what the hell are you doing on the floor? I've calling out for ages. When did you come in?' She would usually try and move me but a few times she'd just let me sleep until I woke up and wandered off.
On most occasions I can feel the need for sleep to creep up on me. I say 'I can feel it coming round again' meaning one moment I'm absolutely fine, the next, I can't keep my eyes open. Then after a while I'm wide awake. As I think I said my sleep is hard to monitor.
I remember once Stephen Fry saying on 'QI' that people who sleep more live longer. I'm not 100% sure about that but if so, I'm going to live for a long time, and most of that time I'll be drowsy.