Let other people witness your actions...

Donald's Commentary on The Handbook of Epictetus #35

When you do a thing which you have made up your mind ought to be done, never try not to be seen doing it, even though most people are likely to think unfavourably about it. If, however, what you are doing is not right, avoid the deed itself altogether; but if it is right, why fear those who are going to rebuke you wrongly?

Commentary

Marcus Aurelius likewise says that we should do nothing that we should be ashamed to admit in public.

Never value anything as profitable to yourself which shall compel you to break your promise, to lose your self-respect, to hate any man, to suspect, to curse, to behave hypocritically, to desire anything which needs walls and curtains. — Meditations, 3.7

This sounds rather like something a Cynic philosopher might have said, perhaps. For Stoics as well, though, what matters most is simply whether an action is virtuous or not, and how others respond is ultimately indifferent.