Why does having a crush make you feel crazy?

The feeling starts in your nervous system. Your pupils dilate, you become short of breath, sweat collects on your palms, and suddenly you can't eat a bite. You're in love—or in lust, at the very least. It's what psychologist Kristina Feeser, a professor at the University of Virginia's College at Wise, calls "activation." The rest of us call it a crush.