I can actually vouch for this, but I discovered it independently for myself. I realized that the nights I couldn't fall asleep were nights my brain kept racing and thinking about different things. Kind of like a wikipedia rabbit hole where my mind keeps racing onto the next tangential thought.
So I found a foolproof solution: Relax all my facial muscles and imagine an empty, black (literally #000) void in my mind's eye.
The physical cue is to be cognizant of your eyes; every time my eyes began to squint, I know it was because my mind was wandering off. I'd reset my closed eyes to be as loose (imagine a very bored expression) as possible and revert back to my black space. As long as I kept fighting the temptation for my mind to wander, and maintain loose eyes, I fell asleep. All anecdotal of course, but I did use this just recently at burning man while soundcamps blasted my tent, and it's nice to see this method validated in this article.
So I found a foolproof solution: Relax all my facial muscles and imagine an empty, black (literally #000) void in my mind's eye.
The physical cue is to be cognizant of your eyes; every time my eyes began to squint, I know it was because my mind was wandering off. I'd reset my closed eyes to be as loose (imagine a very bored expression) as possible and revert back to my black space. As long as I kept fighting the temptation for my mind to wander, and maintain loose eyes, I fell asleep. All anecdotal of course, but I did use this just recently at burning man while soundcamps blasted my tent, and it's nice to see this method validated in this article.