That is what your unconscious part of the Brain does. It is programmed and acts fast but the problem is that it may have over-estimated the danger and acted speedily as if the threat is immediate and decided to throw all its weight to protect you from such danger, then you discover there was no immediate danger and moreover, the defence mechanisms used namely, fight, flight or freeze have aggravated the situation more and caused perhaps Mental problems and Physical Health conditions.
With the repetition of this automated efficient system, in terms of speed, the situation becomes chronic and the potential health conditions are maintained in a chronic way.