mens sana
/ˌmɛnz ˈsɑːnə/ /ˌmɛns ˈsɑːnə/noun
1 mens sana in corpore sano: a healthy mind in a healthy body; in later use frequently specifically with allusion to an approach to education in which this principle is emphasized. Also (occasionally) mens sana in sano corpore.
2Simply: a healthy mind. Usually allusively.
Origin
Early 17th century; earliest use found in John Harington (bap. 1560, d. 1612), courtier and author. From classical Latin mēns mind + sana, feminine of sanus healthy; the phrase given at sense 1 occurs in Juvenal Satires 10. 356.