We all know this intuitively, but ignore the consequences of excess stress.
These effects of stress exist on a bell curve — that is, some is good, but too much becomes bad: As the nervous system secretes more and more stress hormones, performance increases, but up to a point; after that tipping point, performance begins to suffer as the hormones continue to flow. What makes stress “bad” — that is, what makes it render us more pervious to disease — is the disparity between the nervous system and immune system’s respective pace.
Needull in a haystack 