The ultimate ground of our rejoicing can never be our circumstances, even though we as Christians recognize that our circumstances are providentially arranged. If our joy derives primarily from our circumstances, then when our circumstances change, we will be miserable. Our delight must be in the Lord himself. That is what enables us to live with joy above our circumstances. As Nehemiah puts it, “The joy of the Lord is your strength” Neh. 8:10. Perhaps that is one of the reasons why the Lord sometimes allows miserable circumstances to lash us—that we may learn this lesson.…Whatever the mysteries of evil and sorrow, they do have the salutary effect of helping believers to shift the ground of their joy from created things to the Creator, from the temporary to the eternal, from jingoism to Jesus, from consumption to God.
D.A. Carson, Basics for Believers: An Exposition of Philippians, p. 106via NEXT | March 2009 Webzine.