the thing that helped me most and i didn't know about until i read that book is the "don't stay in bed *trying* to fall asleep" bit. if it's been 20 minutes and your mind is still disquieted, get out of bed and do something not involving screens (if possible) and not particularly interesting or engaging. i'll fold laundry or read something dry like marie kondo or a history book. it's kind of amazing how yawny i get and how quiet my mind gets after getting out of bed, after struggling to sleep for 15-20 minutes. usually the second i get out of my bedroom i get tired again 🙃