Asleep or not asleep?
Harry Bosma, 2004
There is particular book that I find remarkable, even though I don't do much with it. It is an advanced book from a tradition that takes some getting used to. I'm talking about the Tibetan Yogas Of Dream And Sleep, by Tenzin Wangyal Rinpoche. Notice it says both dream and sleep. While Christoph Gassmann calls for more awareness in dealing with dreams, Tenzin Wangyal Rinpoche also talks about being aware while asleep.
I tried the exercises once, and it felt as if I hardly got any sleep at
all. That was most likely my own fault. Still, how do you know that
you're asleep when you
have awareness? 
To me, sleep is defined by the lack of awareness. You
loose consciousness, so you're asleep. Apparently, this is not a good
definition of sleep. Tenzin Wangyal Rinpoche says that sleep is related
to the cessation
of sensory engagement. Although he specifically mentions vision, I
assume it refers to all senses. To an extent, because many people use
alarm clocks because hearing still works somewhat.
Here's the problem. If I become conscious of myself in the middle of the night, without vision but with for example feeling myself breathing, am I asleep or am I awake? Hard to tell. There is for example sleep paralysis, which deactivates the usual connection between brain and muscles. That's a good thing, as it's dangerous to move about while asleep. I have often enough woken up from dreams straight into a few seconds of sleep paralysis. That can be scary. The senses don't work, and the muscles don't respond. However, I wouldn't say I'm still asleep.
Another example. I regain consciousness in the middle of the night, feel myself breathing, do not recall any dreams, have no other sensory input, and after say a 20 seconds loose consciousness again. Quite a few older people would complain they sleep badly. Let's bring them the good news that they are advanced practioners of Tibetan dream yoga! The difference probably is that to me - and it has only happened a few times, but hoping for more - it has a pleasant peaceful quality to it. I doubt that people who sleep badly, feel the same way, but perhaps they will after they read the book too.
Still, it would be nice if there was some other sign of being asleep, even if you are conscious. I will let you know when I learn more about this.