From: The Golden Sayings of Epictetus (translated by Hastings Crossley) - from Project Gutenberg.
CLXXII
When you have decided that a thing ought to be done, and are doing it, never shun being seen doing it, even though the multitude should be likely to judge the matter amiss. For if you are not acting rightly, shun the act itself; if rightly, however, why fear misplaced censure?
