You have probably learned/heard in more than one place in your life about the concept of flight, fight or freeze. The idea being we release stress chemicals (e.g., cortisol, adrenaline), increase heart rate, dilate blood vessels, and generally prepare ourselves for action immediately when there is a clear and present danger. Freezing might mean a predator does not see us and moves on, fleeing when there is little probability of being able to overcome the danger and fighting when there is no other choice. We are essentially evolved from pack animals; our instincts and ancient neurological structures mean we are prepared for responses like these innately. Governed by the brain we are alert for danger and risk. It keeps us alive, it is, in essence a necessary mechanism.
A great concern, however, is when this survival mechanism in the brain and the accompanying chemical responses are happening continuously and inappropriately. One of the factors which can clearly get in our way of functioning healthily is inaccurate detection of potential threat. The thalamus/hypothalamus and amygdala interact to detect threat and make (incredibly fast) decisions about the nature and severity of that threat and of course to initiate our fight or flight response.
Have you ever been in meeting, conversation, or other social situation where your heart started racing, blood pounding in your ears and you felt an overwhelming sense of emotion? If so, you might judge the release of your fight, flight or freeze system as inappropriate. Essentially the FFF system has been set off by a false alarm.
One thing that sets off my FFFS is a door banging- a door bangs and there is a short cut straight to my amygdala to warn me of the incoming danger and the thalamus initiates the FFFS- hopefully as the amygdala realizes that there is no actual danger it then signals the thalamus to stop the FFFS and things return to baseline.
Negative thinking can also initiate the FFFS and that is where we should focus our attention. How many of the overwhelming times you feel the rush of adrenaline etc. is it due to an actual clear and present danger? and how often is it simply thinking about things, rather than those things happening right thee and then. You can imagine victims of trauma initiate the FFFS often as negative, and sometimes horrific, thoughts/memories/images pop up.
One thing we can do, is notice this is happening, as when thoughts overwhelm us we are too busy being overwhelmed to notice that this is a set of thoughts and not necessarily reality, or at least not reality right now- we are not in the place where the unhappy memory occurred, we are not running from the sabre tooth tiger right now and this noticing allows the other areas of the brain, especially the pre-frontal cortex to get in on the action and start to use some logic. Some of that logic in response to a horrible memory might sound a little like this: ‘that was an awful situation/thing to happen, and it is understandable why it is sometimes overwhelming to me, but it is not happening right now, these are thoughts not actual reality’
Another thing, which seems counter-intuitive, but can really help, is to not try and push thoughts away, notice they are there and rationalise why they are there (often because it was a horrible experience and the brain is attempting to go back and fix something it cannot). The thought is there, accept it and seperate you from the thought (you are not your thoughts after all) because thoughts come and go and there isn't always a clear reason, we just accept that they come and go and that this does not mean we are crazy, it just means that thoughts ping in and out of our heads.