The Four Brahmaviharas
There are four divine abodes: Metta — loving-kindness, the wish for all beings to be happy. Karuna — compassion, the wish for all beings to be free from suffering. Mudita — sympathetic joy, rejoicing in the happiness of others. Upekkha — equanimity, the balanced mind that is neither pulled toward pleasant experience nor pushed away from unpleasant.
Of these, equanimity is the most difficult and the most essential. Without equanimity, loving-kindness becomes possessive, compassion becomes grief, and sympathetic joy becomes agitation. Equanimity is not indifference — it is the stable ground from which all true love and all true compassion arise and to which they return. It is the open sky within which all weather moves.