Letters 85.16

Besides, if the wise man, instead of despising all causes that come from without, ever fears anything, when the time arrives for him to go bravely to meet the spear, or the flames, on behalf of his country, his laws, and his liberty, he will go forth reluctantly and with flagging spirit. Such inconsistency of mind, however, does not suit the character of a wise man.

Seneca, Letters to Lucilius 85.16, translated by Richard Mott Gummere