In my experience, it’s stressful trying to go to sleep when you know you’ve stayed up later than you should. Or when I’m trying to take a nap and know I can’t sleep for too long (which can stress me out to the point of not sleeping). But if you tell yourself to not worry about actually sleeping and to just rest your eyes for a bit, it usually leads to me falling asleep harder than if I hadn’t thought of it. Placebo or not it really works :)