I get into a state of anxiety sometimes where thinking almost anything will trigger a cascade of neurotic thoughts. This has led to many sleepless nights. Whilst it doesn't always work, I found one effective technique to make your brain sleepy is just try to think of the most boring, unstimulating ideas. For some reason, I find it really effective to think about plain flat colors like brown or grey. I'm not getting much inspiration to proceed with an inner critical monologue when I think about the colour brown or grey. Not objects in these colors, just the actual colors. I imagine myself in a sea of that color and it is calming and neutralising, for reasons I don't fully understand.