"A benevolent eye" or "a good eye" is the Hebrew expression for not begrudging people that which they have. The corollary is that the way of life to avoid is having "a malevolent eye," i.e. begrudging people what they have.
In Yiddish, the equivalent of "a benevolent eye" is "to fargin," as in the expression "I fargin him with all my heart." There is no equivalent word in English for fargin, and it can only be translated in the negative, i.e. to fargin is to not begrudge. As noted in 23 Adar, the absence of a word in a language may be a clue about something in that particular culture. Is it possible that much of the English-speaking world knows only how to begrudge, but does not know how to fargin?
Be that as it may, Rabbi Eliezer considers "a benevolent eye" much more than just a desirable trait. He considers it an all-encompassing feature that constitutes the optimum adjustment to life. Other people may possess more material wealth. Their children may have achieved more. They may enjoy better health. In whatever way other people may be more fortunate, Rabbi Eliezer sees farginning them as the character trait that will make all other traits fall into line. Conversely, not farginning is a trait that so permeates one's personality that everything one thinks, feels, or does will be negatively affected.
Perhaps not everyone can rejoice in what others have, but we can all fargin.