I have had some luck with this method [0]: "The trick is reportedly used by the US army to help them fall asleep when in situations that are less than peaceful, such as on battlefields." It has some similarities to yours, but some interesting differences as well. I've modified it a bit to say “don’t think, don’t think, don’t think” to myself over and over for a minute or two instead of 10 seconds

https://www.independent.co.uk/life-style/fall-asleep-two-min...