It needn't be an incident. I first learned the term in the cockpit of an airplane. It was all about preventing an incident. It involved 3 axis of movement (both of my airplane and others), sounds of the engine, wind noise, a dozen panel indicators, my exact position along a planned course, a precision approach to successfully terminate the flight.
It still governs the way I drive, walk, bike, boat, etc.
When I dine out, my choice of locale and restaurant somewhat relieves me of such highly tuned senses.
At home, my cameras, my dog and my neighbors relieve me if even more
As Jeff White said, man cannot live at heightened states for the majority of his days. I make it count.
