The phrase "fight or flight response" is probably one you've heard. The phrase was coined over 70 years ago by physiologist Walter Cannon and refers to the body's natural response to stressful or threatening situations.
When you're faced with a stressful or even dangerous situation and begin to feel anxiety or fear, your body automatically reacts. For example, your heart rate may increase, your muscles may become tense, and you may begin to sweat and have narrowed vision ("tunnel vision").
This occurs because of stress hormones being released in the body and are all part of the fight or flight response, which prepares you for taking immediate action. It is preparing you to either flee, freeze (like a deer in headlights), or fight. Essentially, this response helps keep us safe, and alive! But, there is a difference between real and imagined threat and sometimes your body can not tell the difference between the two. If you interpret a situation to be threatening even when it's not (such as public speaking or a crowded store), your body's fight or flight response will still activate, or "kick in", as though the situation really is dangerous.
When the fight or flight response is frequently being activated, even when it's not necessary, it becomes a problem. This is especially true for people suffering with Post Traumatic Stress Disorder (PTSD). If you have survived a trauma (such as child abuse or military combat), you may no longer experience the world as being a safe place. Instead, you may feel like danger and threat is everywhere, all of the time.
After surviving a trauma, your body no longer needs the fight or flight response. However, with trauma it is common for the response to get "stuck" - leaving you in the constant state of fear and anxiety, in what feels like an unsafe world.
This is called hyperarousal. You may not even know that you're stuck in the fight or flight response because it's just become your normal way of life. But, if you've suffered a trauma (no matter how long ago) and feel like you are only surviving, not living - this is a good indication of being stuck.
With therapy, it is possible to restore your fight or flight response system to normal so that it works only when needed, instead of in overdrive!