The word euthymic derives from the Greek word euthymia. The prefix “eu” means good, well, or balanced.
The word thymos in ancient Greece was considered the seat of the soul, the center of raw emotion, passion, courage and internal fire.
To the ancient Greeks, being euthymic didn’t mean being a flat, sterile robot.
It meant having a well balanced soul, a sort of state where your inner fire is burning steadily, neither raging out of control nor completely extinguished.
Euthymia is a state of fluid emotional health.
“Cheerfulness [euthymia] arises in men through moderation of enjoyment and proportion in life.” -Democritus