If you are or have been a student you will definitely recognize this symptom. You are studying some interesting (hopefully) or uninteresting (hopefully not) material and while you feel very alert mentally your eyelids will just start edging downwards until they “happen” to close. This cannot be beaten with force of will, it will just keep happening and happening. To “treat” this problem, or really symptom, you have to either take a nap or go around the block to get some fresh air. The real nasty thing about this is that it happens quite a lot and it does so even though you are getting enough sleep…or so you may think. I just happened to remember this and that I have not been afflicted with this problem for about 1-2 months, while it used to happen quite a bit. And I study jsut as much, no more than earlier. I know something else that happened two months ago as well – I went vegan, and then raw 1 month ago. This is just so amazing. On that note I do not feel like it was two months ago I had this problem or dropped meat – on the perceived-time scale it feel more like years – I was another person then.