# Forget Everything And Run (FEAR) A automatic reaction of the hindbrain. It's the fight-or-flight response. It's an automatic reaction triggered by the oldest part of our brain, the one that is always on the lookout for danger. When it senses a threat, it triggers the fight-or-flight response. This response is automatic and almost instantaneous. It's what makes us run away from a lion or fight back when we're attacked. It's what makes us freeze when we're scared. It's what makes us panic when we're in danger. It's what makes us anxious when we're stressed. It's what makes us worry when we're uncertain. It's what makes us doubt when we're insecure. It's what makes us hesitate when we're unsure.