In many fields of medicine and science it hase been found that a
"little bit of bad does a lot of good". A topical example is
"preconditioning" tissues to avoid reperfusion injury. i.e. cut off
the blood supply for a short while (to give a gentle shock) enables
a tissue to withstand subsequent longer loss of blood supply.
So it could be with stress and the immune system - although heavy
stress can be debilitating, a little bit could "tune up" the system
Relax!
Phil Ledger