Someone is spreading a story about you that is demonstrably untrue.

Take this situation apart. Each piece goes in one box: yours, or not yours. There is no third box, and almost nothing falls in one piece.

Yours

Correcting it once, and then living on.Where it makes sense, you calmly put down the facts. Whoever keeps correcting after that makes the story bigger than it was and hands his days to something he does not steer. Your character is what you do, and it speaks longer than the story.
How often you retell the story yourself.Whoever keeps presenting the lie to everybody in order to refute it has become its most diligent distributor. One correction in the right place is a rebuttal; ten repetitions in the wrong places are advertising.

Not yours

The story, its spread, and who believes it.That lives in other people’s mouths and heads, and you hold no key to either. Your reputation is what others agree about you; that meeting is held without you.

The reasoning. The story belongs to its tellers; the answer to it is yours, and the best answer is short.

If someone tells you that a certain person speaks ill of you, answer: he did not know my other faults, or he would have mentioned those too.Epictetus

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