for me, the outdoors is a time for reflection and that soul searching stuff. So by design, my mind is wandering. Except I know I need to be well rested for the following day, and I gotta tell my philosophy brain to STHU.
When sharing a tent with one of my young nephews, I'm instinctively in paranoid protective mode, and wake up every 2 hours. Usually it's a scavenger squirrel snapping a twig.
When sharing a tent or separate tent with my adult friends, I fall asleep right after sunset, I snore loudly and solid for 6 hours, then wake up at 4AM to photograph the sunrise.
I tried Melatonin from the vitamins shop, it gave the seasickness vertigo feeling without falling asleep.
A Tylenol muscle relaxant helps, but might also consider your fav alcohol night cap, like 1 shot of yagermeister or fine aged whiskey or teq, in a tiny container from Lawson Equipment. I don't know the guy, he posts here though, but I like his website. he has an 8 oz flask, but these days I'm alc wuss, I'll settle for the alc in a one ounce Mini Dropper Bottle. just enough to yawn, not pass out and vomit.