Rejoicing is an antidote to being jealous of others' good qualities, abilities, and virtues. It's also an excellent antidote for depression. Rather than thinking about how awful the world is, how terrible we are, how hopeless the world sees, we make our mind happy by thinking of all the positive qualities that we and others have and all the beneficial actions we and others have done. Rejoicing creates great positive potential (merit) and makes our mind happy and optimistic. It also enables us to have a more realistic view of the word by seeing the goodness of living beings, not just their suffering and defilements.

Thubten Chodron, Cultivating a Compassionate Heart