mens sana in corpore sano
[mens sah-nah in kohr-poh-re sah-noh; English menz sey-nuh in kawr-puh-ree sey-noh]
a sound mind in a sound body.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
c.1600, Latin, literally "a sound mind in a sound body," a line found in Juvenal, "Satires," x.356.
Mens sana in corpore sano is a contradiction in terms, the fantasy of a Mr. Have-your-cake-and-eat-it. No sane man can afford to dispense with debilitating pleasures; no ascetic can be considered reliably sane. Hitler was the archetype of the abstemious man. When the other krauts saw him drink water in the Beer Hall they should have known he was not to be trusted. [A.J. Liebling, "Between Meals," 1962]
Online Etymology Dictionary, © 2010 Douglas Harper