I copied this from here:
The fight or flight response is the response of the body to a perceived threat. When faced with danger, the body releases hormones such as adrenaline and cortisol. These hormones give us a burst of energy and strength by increasing the heart rate, slowing digestion and directing blood to major muscle groups. Although the response is helpful in cases of physical threat (such as needing to run away from a bear), it is inappropriate and maladaptive when it occurs in social or performance situations, as is the case with social anxiety disorder.
You’re telling me?