Stress, throughout the history of our species, was traditionally associated with a threat. The evolutionary response to such stimulus is therefore the immediate release of three different hormones in sequence, each affecting different parts of the body: Adrenaline, noradrenaline, and cortisol.
The amygdala, the part of the brain that drives our most basic survival instincts, is triggered immediately upon release of these hormones. The amygdala will then direct your reaction as a response to the threat, primarily fight or flight. It will also determine if you keep it together or completely lose it.
The amygdala is also associated with emotions. With a female brain being more empathic, and a male brain more analytic, a male’s reaction to a threat is far less emotional and far more effective than that of a woman. Incidentally, due to different parts of the amygdala activated in males and females, a male will also be less reactive to pain typically traditionally associated with a threat (as in combat and fighting).
For a better and more effective response to stress, the brain must be trained, and continuously exposed to specific threats, in order to fine tune or even determine or optimize reactions. Hence the essential need to continuously train for combat and other threats.
However, if the brain is constantly exposed to stress, you lose the ability to respond to such threats effectively. To make the matter worse, our brain does not really differentiate actual existential stress that is the result of a threat to our immediate survival, and artificial modern life stress, such as gaining aneurysms from social media.
While it is important to train and condition yourself to be able to face and handle all threats, it is equally important to return your brain to a relaxed state on a regular basis. This includes fundamental lifestyle changes to disengage from every day stress, such as exposure to liberals, social media, or the state of our civilization.
If you cannot relax, your brain will not be able to react effectively when faced with actual existential threats. Relaxing is therefore a matter of survival.