My heart raced. Fear is an aspect of our existence that we share with many other creatures. It's wired right into the archaic brain that birds and reptiles have and we, too, still have. There is a thimble-sized thing in the center of the head, and from that primitive command center, the control filaments run right on up to the where the stress hormones are controlled. Eventually it gets to our cortex, where we do our thinking, but not right away.
Fear begins in at least two different circuits in the brain.
That's the brain processing threatening sights and sounds in milliseconds, and it's all non-conscious. Fear does get to our higher cortical thinking capacities but that takes a lot longer because the simplest thought takes full seconds to develop. So we experience fear in a conscious way only after we have first processed it in an unconscious emotional memory-bank. That memory-bank, which operates, as I say, outside the range of consciousness, is part of that ancient amygdala, and it learns and memorizes the fearful stimulus with tremendous speed and tenacity. One terrifying experience records a memory that lasts a lifetime.