Paul wanted the Phillipians to learn how to live their lives pleasing to God. The result of them having discernment would be a closer relationship with God and a more loving relationship with their families and friends. Selfishness would make them only live for themselves and to get and never give. We can do alot of "good" things and look good to people around us. We can settle for good when God has greater things planned for us. He will give us the discernment to know what the best is.