That is a classic quote from Epictetus pondered in a post by the same title from Philosiblog.
The simpler cousin of that comment is the concept that if you receive criticism, you ought to evaluate which parts are correct and make the appropriate changes. You are free to ignore those parts of the criticism which are invalid.
When the comment about you involves lies, the above quote suggests you evaluate whether there is any truth in the comments. If so, then you have some work to do.
The difficult part is when the evil spoken of you is a lie.
The above quote suggests chuckling at the foolishness of the comment and letting it go. Laugh at it:
Being able to laugh, even if it is done so as not to cry, you are better off than if you had not laughed. When people treat you badly, they expect a response. Laughter is not the response they expect. If for no other reason than to annoy them, laughter is an excellent response.
The post then suggests looking at the motivation of the person telling lies about you. Perhaps the person is misinformed. Or more seriously, perhaps the person knows exactly what they’re doing and is just trying to get you mad, or distract you, or generate a response that in turn makes you look bad. Being able to ignore it with a laugh is a superb counter to whatever bad intent the other person has.
The great closing paragraph:
Your attitude will help define your altitude. If you’re always looking for ways to be annoyed or hurt by the words of others, you will always succeed. And you will be miserable, both as a person, and to be around. Instead, I would urge you to find a way to laugh it off. Things won’t always go well, and laughter will help.
Great advice. Now to live it consistently.
Check out the whole post. It will be well worth your time.