I've found that envy is proportional to our own insecurity, self doubt, unhappiness with our own lives, etc.

The more confident, self assured, and happy I became with my own life, the more the envy went away. The more I became happy for that person's success. Also I've found that there more I know and like a person, the less envy I felt.

At least for me, getting married helped with this big-time.