It seemed hilarious to me, but nevertheless I have tried that this night. I came to Z (even though it became hilarious to think about something for X for example) and still was awake
But it wasn't exactly such a hard night this time like the last one, maybe at least made me a bit sleepier.
Maybe you need to double-check your "sleep hygiene" then. The same professor that taught me that exercise said she tells all of her clients that have problems sleeping to do ALL of the following:
1) Have a bedtime and stick to it.
2) Have a bedtime ritual: e.g. brushing your teeth, washing your face, putting on your PJs, say a little prayer, and hop into bed.
3) There are only TWO things you should be doing in your bed: Sleeping and I think you can figure the other one out. Don't study, read, play your gameboy, or do ANYTHING other than those two things. If you simply MUST do something in your bed (i.e. it's the only place to sit in your room) then put your head on the other side of the bed.
4) Crucial: If you are lying in bed for more than 15-20 minutes and you still can't sleep, get out of bed and do some of the things other people have mentioned (crosswords, read a book, etc.) for about 10-20 minutes before going back to bed. Lying wide awake in bed feeling frustrated and miserable is not going to help you go to sleep.
5) You could try exercising a more than six hours before bed, but never right before you plan on sleeping. (This is generally what they suggest to people with insomnia)
6) Avoid taking naps during the day if you can.
7) Avoid caffeine, nicotine, and other stimulants before bed.
8) Use the exercise from my previous post if you are feeling anxious or stressed out.
There you have it: Sleep Hygiene.