Can you describe the fight-flight reaction, do you mean the push/crash reaction described in some of the pacing theories?
My experience is that I am not well enough to do the push part.
Downturns in my health can be caused by reactions to drugs/supplements/regimes etc that don't cause an initial improvement. For examples a juicing diet caused an immediate downturn in health and functioning. A graded exercise program caused an immediate downturn.
Things that have helped me are few and those that do don't cause extra energy that boosts me to an enormous extent. for example probiotics helped my stomach but didn't give me extra energy. Valtrex helps with sore throats, glands but does give me extra energy.
My experience is that very little helps me or gives the extra energy to have a "push" or a "fight-flight" reaction.The things that have boosted me and caused extra energy/exercise are so few that their effects are over with years in-between.
For example, Lyrica helped with the muscle / neuropathic pain but makes me hyper with a restless energy so I only take it occasionally. Armour thyroid gave me extra energy for a month but then stopped that effect. I recovered back to my "normal"position after that.
I guess if someone was taking a lot of stimulant drugs and was able to artifically energise their body, over and over again, then they would crash big time afterwards?
I'm sure I'm stuck in the fight or flight mode (increased sympathetic nervous system activity)
In my case this increased sympathetic activity is caused by low blood volume:
Norepinephrine before saline infusion: 3.78 nmol/l
Norepinephrine after saline infusion (increases blood volume): 2.66 nmol/l
Beside psychological stress there are a lots of things that can increase you sympathetic activity like:
Low cardiac output
Low ambient temperature
Low blood volume, dehydration
Low blood sugar (only epinephrine)
Alcohol or opioid withdrawal syndrome
A chronic state of fight or flight is not desirable. It decreases the blood flow to the gut withs causes dysbiosis and leaky gut. I don't know if it also causes bad side effect
I've suffered from this 'fight-of-flight' state all my life, overreacting to any stresses, not only emotionally but also physically, with abdominal cramping, diarrhea, increased urination, dehydration, sweating, racing heart, with any stress, every day.
True story: it all disappeared three years ago within a couple weeks of going gluten-free / casein-free.
I don't have an explanation to offer and maybe I am a unique case.
I've always described some of my emotional states that way. I've never heard anyone else sum it up that way so i'm pleased that i'm not alone in my thinking. I've always linked it with a faulty immune system reaction.