I Don't Get It

Okay, so I go to bed last night knowing I have to be up at 6:00 in order to get to school on time. I get to bed at a decent hour, around 10:30 or 10:45.

I wake up at 4:15 needing to go to the bathroom. It takes about two minutes.

So why should it take me almost 45 minutes to get back to sleep?

And what's with all the music going through my head as I try to think about nothing and return to blissful slumber? "After All" by Peter Cetera and Cher, fifteen seconds of which I heard three days ago? "Back In the USSR", which I can't recall having heard at all in the last few months? What's with the unsolicited mental soundtrack?

I don't get it.