One of the main themes of Philippians is joy.  What caused this joy?

Philippians 1:4 "always offering prayer with joy in my every prayer for you all"

Do we find joy in prayer?

Philippians 1:25 "Convinced of this, I know that I will remain and continue with you all for your progress and joy in the faith"

Do we find joy in the faith?  In the gospel of Jesus Christ?

Philippians 2:2 "make my joy complete by being of the same mind, maintaining the same love, united in spirit, intent on one purpose."
Philippians 4:1 "my beloved brethren whom I long to see, my joy and crown"

Do we find joy in our Christian family?  Do we find joy in the unity and oneness of the followers of Christ?

Philippians 2:17-18 "But even if I am being poured out as a drink offering upon the sacrifice and service of your faith, I rejoice and share my joy with you all. You too, I urge you, rejoice in the same way and share your joy with me."

Do we have joy suffering for the 'service of the faith'?  Do we share our joy when suffering for the sake of His name?

This is not an exhaustive list of all the references to joy in Philippians, but do our lives model what Paul exhorted the Philippians to do?  Do we find joy in these things or something else?