Chazal (Berachos 20a) teach that the progeny of Yosef, like Yosef HaTzaddik, were not affected by the power of ayin hora, evil eye. This is in connection with the above pasuk, “A charming son is Yosef, a charming son to the eye.” Yosef never sought to enjoy that which was not his (such as Potifar’s wife, who made every attempt to seduce him), thus, the evil eye affected neither him nor his descendants. Why should one suffer because another person is envious of what he possesses? Should one conceal himself and his good fortune from the public eye, just because someone might be jealous of him?
In his Michtav M’Eliyahu, Horav Eliyahu Eliezer Dessler, zl, explains that the dynamics of “evil eye” is ethical in nature. The blessings that Hashem bestows upon a person should not serve as a source of anguish for another person. If one permits his blessings to cause pain to another Jew, especially if he openly flaunts these blessings, he is risking Divine retribution. He can, by his self-absorbed actions, incur Divine judgment against himself, as well as a re-evaluation of his suitability for and worthiness of the good fortune of, which he had been the recipient.
One who lives his life out of the public eye and does not call attention to what Hashem has favored him with, will not be envied by people and, as such, will have a greater “shelf-life” for his good fortune. Fish are covered by the water which is their home and, as a result of their habitat, do not interact with land-based creatures. Ayin hora does not affect them. Likewise, one who is satisfied with living for himself and not interested in “gouging out the eyes” of others has a better chance of endured status for his satisfaction in life.