The nerves of the gut know when essence is too low.
They steal essence from the brain.
Fuel gets low. The ceiling gets low. Salary gets low.
Clear thought decreases.
Turbulence increases. Fatigue increases. The scorn from the corner office increases.
A pilot, told to ignore a broken nav light,
Feels his essence drain away with the daylight.
Cancel and lose my job?
Fly and lose my license?
Worse, fly unlit and strike another craft?
No essence remains after questions such as these.