Greek students, as we take a brief look at Philippians this semester, please do not forget: The letter is not an appeal for joy. It is an appeal for unity. It is from that purpose that there arises the great Christological paragraph in 2:5-11 that speaks of Christ's selfless humility. Only if we keep this in mind can we understand Paul's appeal to two women who had been quarreling in the church (4:2). Philippians is an appeal to maintain the unity of the church or it is nothing. Joy is merely the by-product of selfless living.
Brethren, we are a band of brothers, bound together in one Spirit (1:27).
Don't let the world see us fighting each other. The fact that we are all "in Christ" should keep us in unity with one another.
(For my detailed study of this topic of unity, go here.)