The Fight or Flight response was named by an American psychologist, Walter Cannon, when observing an animal's digestive system under stress. This response happens when adrenaline and norepinephrine are released from the adrenal glands. Your fight or flight response can kick in during any stressful event, even good ones. This response causes an increased heart rate, high blood pressure, and breathing rate. Your fight response physically prepares you for a fight while your flight response prepares your body to run away from something.
When your brain believes that it is threatened and that it can overcome the threat, it will release the fight response. In this response, your brain releases adrenaline. Once this adrenaline is released, you can feel your jaw tighten or your stomach knot due to the fact your brain wants to fight something. Some people act on this response while others keep it to themselves. Grounding yourself through breathing helps to relieve the fight response because it reminds your body that you're safe.
The flight response can occur when your brain feels threatened and believes you cannot escape. This causes your body to prepare to run for an extended period of time. After adrenaline and norepinephrine are released, your body begins to feel restless and you feel like you have to move. Most people in their flight response cannot resort to the correct thinking process to calm themself. To calm yourself during this response, you should listen to your body and go for a run or do deep breathing exercises.
In both these stress responses, they cause people to lose their senses and thinking processes. It becomes hard for some individuals to cope with intense emotions and impulses. Once you learn how to identify and cope with triggers you can avoid your fight or flight mode. If you find it difficult to identify your triggers, go to a psychologist or therapist who can help you to identify your triggers and cope with them.