Those who founded America lived under duress when they sailed the seas, and were under constant stress from foes within and without as they pressed onward from East to West. They had the stress of forging a new country economically, socially and politically. History recounts the story of the Donner party attempting to reach California, only to be faced with the winter wilderness weather, and to resort to cannibalism among themselves to stay alive. That's living in crisis. Our ancestors did not have an easier life simply because it was less sophisticated.
Stress can come from a variety of sources.
It can be from sources inside or outside of ourselves, self-induced or the result of adversity. A certain amount of pressure is necessary to fine-tune a guitar, piano, business or person. It's both normal and necessary to healthy living. Too much pressure will snap the string, break the person, or ruin the business. The ability to withstand adversity comes from the character within.