Stress is our body's natural biological response when triggered by a threat of imminent danger or a demand. This response has evolved over the millennia (and continues to!) to a perfected system-wide series of chemical releases and reactions for optimizing our survival.
Our typical reaction includes:
Increased focus and attention
Increased heart rate to optimize oxygenation
Shift of energy and strength to particular areas of the body
Suppression of the immune and digestive systems. (Who needs to fight off a cold or finish digesting that meal when we ourselves may become a meal?)
Converted energies for strength and stamina
After a threatening event, our systems return to normal and we carry on digesting food, fighting off potential illness, and planning our next steps.
All of these reactions, honed over tens of thousands of years, support an appropriate response for physical danger--fight, flight or freeze. It is only in our most recent generations that our experience with stress has shifted from a real need to protect our physical bodies to a perceived need to protect our sense of self.
But our biology automatically responds the same--whether there is an actual threat or a perceived threat--and today, it can lead to chronic health problems.