I think envy is a tool we have as a result of evolution. If you don’t buy the next best car or that shiny thing (house, jewelry etc), the sexual partner may choose the one who does instead of you. I think envy is the arms race we developed so that we try hard to find a partner so that your gene pool continues to exist. I am not sure we can do what the author says about “knowing oneself” as there are very so many ways to interpret it. I think we are way more complicated to be able to know oneself since we have 3.5 billion years of evolutionary history. Our unhappiness may act as a counterweight so that we may choose to tame our envy.