Of all the characteristics of ordinary human nature envy is the most unfortunate; not only does the envious person wish to inflict misfortune and do so whenever he can with impunity, but he is also himself rendered unhappy by envy. Instead of deriving pleasure from what he has, he derives pain from what others have.
Source: The Conquest of Happiness, 1930, chap.6:Envy<
More info.:http://russell-j.com/beginner/HA16-030.HTM