Abhidhamma In Daily Life
Factor 10 - Mudita
The feeling of sympathetic joy at the success, welfare and prosperity of others is called Mudita. In life, evil-minded people experience envy, jealousy, greed, etc. when someone gains popularity, promotion, wealthy, education, status, position, etc. but noble-minded people, when seeing or hearing of such events, feel glad; they applaud the success of other people with sincerity. They reason life this: "Oh, they gain wealth, power and success and popularity because they have sown the seeds of kusala-kamma, good and noble actions in the past, and now they are reaping their due harvest." This is true Mudita.
False Mudita means excessive joy and gladness at the well-being of one's own relatives and friends. This gladness resembles Mudita but actually it is a false one. Such extreme joy even to the point of tears is known as piti somanassa, which is associated with tanha and lobha. But all such gladness and joy must not be taken as false, because there can be genuine Mudita too.