Bowmen bend their bows when they wish to shoot: unbrace them when the shooting is over. Were they kept always strung they would break and fail the archer in time of need. So it is with men. If they give themselves constantly to serious work, and never indulge awhile in pastime or sport, they lose their senses and become mad.

The History of Herodotus: A New English Version, Ed. with Copious Notes and Appendices (ed. 1866)