why was wang lung afriad of hus feeling of good fortune?

Wang Lung fears the Gods will punish those who feel too fortunate. Everyone in town congratulates Wang Lung on having a first-born son. He rejoices at his good fortune. However, he soon grows wary: "It did not do in this life to be too fortunate" (40). He thus decides to buy some incense for the gods, to ensure his well-being and that of his family.