I listened to a shiur this evening that said to say that to protect oneself eternally from ayin hara.
Because Yosef did not covet, his reward was eternal protection from the ayin hara, which extended to all of his descendants.
How can I say that I am a direct descendant of Yosef ha Tzaddik? Is that not a lie?
Well all can say this, for b’nei Yisrael is not only the children of Yaakov but also known as the children of Yosef.
Thus you can honestly [and should, according to this teacher on Torah Anytime] say that you are a descendant of Yosef ha Tzaddik. It’s in the Gemara. The ayin hara won’t be able to harm you B”H.