Bertrand Russell's The Conquest of Happiness is probably not a very deep book, but here and there in the book Russell does give some good advice. The following is what he says about envy:
Envy, in fact, is a form of vice, partly moral, partly intellectual, which consists in seeing things never in themselves but only in their relations. I am earning, let us say, a salary sufficient for my needs. I should be content, but I hear that some one else whom I believe to be in no way my superior is earning a salary twice as great as mine. Instantly, if I am of an envious disposition, the satisfactions to be derived from what I have grow dim, and I begin to be eaten up with a sense of injustice. For all this the proper cure is mental discipline, the habit of not thinking profitless thoughts. After all, what is more enviable than happiness? And if I can cure myself of envy I can acquire happiness and become enviable.
I would emphasize the word 'habit'. Once you acquire the habit, you don't have to struggle with envious thoughts.