I've been on a bender of reading Josephine Tey recently. I don't like mysteries, usually, but I just discovered her, and for some reason I've really been in the mood for her books.
In The Singing Sands, I came across a counter-intuitive trick for falling asleep. I've tried it now, myself, a few times, and it really works.
He put the light out, and resorted to his own cure for insomnia: pretending to himself that he had to stay awake. He had evolved this long ago from the simple premise that human nature wants to do the thing it is forbidden to do...He had only to begin pretending that he was not allowed to go to sleep for his eyelids to droop. The pretense eliminated in one move the greatest barrier to sleep: the fear that one is not going to, and so left the beach clear for the invading tide.