when you are lying in bed, tell yourself what you are doing.
yes, it seems silly, but if you arent thinking about going to sleep, you will fall asleep. you can still think about other thoughts, but tell yourself every 5 seconds, "I am falling asleep to wake up at 4 am"

it seems like this may not be necessary, but it IS.. the brain is going through 10k thoughts a second, so how else would you expect to remember your trying to go to sleep.

EDIT:
and ALWAYS say the repetitive sentence in a positive way. I AM falling asleep. I WILL wake up tomorrow at 4. it works everytime.