I used to have the same sleep problem (head won't stop racing), and mindfulness exercises throughout the day have greatly improved things for me. In a way it feels like the ability to turn it down for a time, long enough to get so tired it doesn't start back up again.
One trick I found myself is to visualise things in the noise from your closed eyes. Try to interpret something you can vaguely see, and then try to visualise it. This imposes a kind of clear image for a short duration for me, from which I try to see and visualise something else in there and so on, kind of like a visual association chain. That really gets me sleepy after a couple of minutes!
> visualise things in the noise from your closed eyes
Ooh, the visualization whirlwind. This is the first time I’ve ever hear anyone talk about it or had to give it a name. At least for me it’s just tons of images flashing before my eyes, rapidly changing, only tenuously guided by my mind.
Imposing the images works for me similarly to when you "can't unsee" something. Like when you start seeing something specific in a generic shape or pattern, like with clouds. I tell myself that I see something, which makes me actually visualise it.
One trick I found myself is to visualise things in the noise from your closed eyes. Try to interpret something you can vaguely see, and then try to visualise it. This imposes a kind of clear image for a short duration for me, from which I try to see and visualise something else in there and so on, kind of like a visual association chain. That really gets me sleepy after a couple of minutes!