"The Tibetan Buddhist tradition also speaks of empathetic joy, but it places even more emphasis on rejoicing in virtue, which is the root of happiness. They say this is a direct antidote for jealousy, inasmuch as jealousy is the inability to bear another person's happiness and success. Note that in the Theravada practice, the first step is focusing on a joyful person other than yourself. In the Tibetan Buddhist practice of rejoicing in the good, it's perfectly appropriate to start with yourself. This is a tremendously rich practice, and it's so simple. There's no notion of achievement, you just do it and it's immediately beneficial."
The Four Immeasurables Practices to Open the Heart
Alan Wallace on how rejoicing in the happiness or success of another person is an antidote to jealousy.