When a traumatic experience occurs, our minds and bodies immediately go into overdrive to try to resolve the overwhelming system-overload that the experience creates within us.
If you are a Star Trek fan, think of this as putting your shields to maximum capacity in order to ward off external enemy attacks.
Adrenal functions are impacted, digestion and other important bodily functions are suppressed, and you immediately go into fight, flight, or freeze mode.
After an attack is over, and you have survived the battle, however, your overdriven system has a hard time calming down.
The danger that you experienced, you feel, is still lurking, waiting in the shadows to attack, like the Ferengi (more Star Trek reference), poised to stir up some trouble at anytime instead of peacefully existing in your shared galaxy. After all, you think, “an attack could happen again.” Did the first torpedo, and then the second torpedo, and then the fires that it created, not just come into your life in the blink of an eye, or last for a long period of time? One day you were going about your day coursing curiously through space and time, and then, in a moment, you were under direct threat or attack.
This cycle of hyper-vigilance, as you are simultaneously working to heal any damage left behind from battle, keeps your shields at maximum capacity at all times. Now you keep your shields up, draining power, for reasons beyond warding off an attack, and this constant overdrive (just to feel and be safe), over time, completely fatigues your vessel, leading to worn out gears and functions, and to the development of serious issues that will lead to a great deal of suffering in the long-run if not fully addressed.