You mention the original reasons for the feeling; the fight or flight mechanism. A fine tuned mechanism that evolved to near perfection over millions of years.
Whenever there's a gap between what the machine (body) was "designed" for and the environment it is presently in (2016!). I believe there's a lot of potential is just putting that machine back in its environment.
So picture a fish out of water. That's us today! Put that bitch back in its aquarium son!

I know there's a LOT a stuff coming out that starts to blend the Paleolithic lifestyle while still benefiting from the modern era.
I won't go into too much detail but things like:
-using candles after sunset instead of electricity
-using f.lux on your devices
-getting at least 20 minutes of sunshine every day
-walking more
-touching people (appropriately!) for the oxytocin
-socializing
-eating stuff that doesn't mess with hormone balance
-some physical activity that makes you deal with stressful situations (my BJJ biais is no doubt apparent here but this actually USES the fight or flight mechanism in a scenario where it's as close to it's design as possible. The endorphins I feel after jiujitsu alone are incredibly relaxing)

I'm curious if you've explored this. Put that fish back in water (: