As in walking it is your great care not to run your foot upon a nail, or to tread awry, and strain your leg; so let it be in all the affairs of human life, not to hurt your mind or offend your judgment. And this rule, if observed carefully in all your deportment, will be a mighty security to you in your undertakings.

Epictetus his morals: with Simplicius his comment (ed. 1700)