You've fallen asleep countless times and you desperately want to know how you did it, but, of course, you can't remember it.  The reason you can't sleep has nothing to do with how many noises there are or how much silence there is.  It has nothing to do with what you ate before bed or how much sleep you got the night before.  The reason you couldn't sleep is that you were anxious or worried.  That's why you can't sleep when you know you really need the sleep for the next day.

Even being anxious can become worry and worry is like an acid in your system.  You can't sleep because your body is fighting for its life.  The only way to sleep is to calm down.  How?!  Well, you need to relax and think of something specific, like a place but NOT an event.  You can count sheep if you want and maybe you'll just get so bored that you'll fall asleep, but what I do is picture something in my mind, something that isn't what will happen or has happened, but something like a house or a place in a dream that you had.  The idea is to start yourself dreaming again.  So far, I don't think I've ever bored myself to sleep.  I remember dreams, most of which have to do with other places.  If I even start to think about why I'm worried or what I'm anxious over, then I can't sleep.  My sleep comes from dreams, not exhaustion.  I'm sure lots of people's sleep comes from exhaustion.  That's just not the way it works for me and it may not be the way it works for you.  There's nothing like waking up well rested and ready for another day.