Eustress

The term eustress means "beneficial stress" -- either psychological, physical (e.g., exercise), or biochemical/radiological (hormesis).

The word was introduced by endocrinologist Hans Selye (1907-1982) in 1976; he combined the Greek prefix eu- meaning "good", and the English word stress, to give the literal meaning "good stress".  The Oxford English Dictionary traces early use of the word (in psychological usage) to 1968.

Eustress is the positive cognitive response to stress that is healthy, or gives one a feeling of fulfillment or other positive feelings.  Hans Selye created the term as a subgroup of stress to differentiate the wide variety of stressors and manifestations of stress.

-- From Wikipedia, the free encyclopedia