It's a threat response. Right before we go to sleep, our brain goes into a state of hypervigilance because back when we were living in caves, sleep was the time we were most likely to get eaten by saber-toothed tiger. So now we lie in bed staring at the ceiling, feeling that anxiety race through our bodies because we're waiting to be attacked by a predator that hasn't existed in 10,000 years.

Kristin