The only times I struggle to fall asleep are when I've consumed any amount of caffeine (or other stimulant) within ~8hrs of attempting to sleep. Doing a couple

The only times I struggle to fall asleep are when I've consumed any amount of caffeine (or other stimulant) within ~8hrs of attempting to sleep. Doing a couple sets of pushups every morning and evening makes eyes closed -> passed out happen more quickly, especially if I otherwise didn't do anything active throughout the day. Sleep comes very quickly if the day was spent mountain biking, hiking, or digging with the pickaxe and shovel. If you're caffeinated/energy drink fueled and sedentary at a desk all day, expect to stay up. Preventing that is a simple matter of cut down the stimulants and get a bit more physical activity. I feel like this is stating the obvious though, YMMV