Because you did not serve the Lord your God with joy and a glad heart…..therefore you shall serve your enemies. (Deut. 28:47-48)

Serve the Lord with gladness (Psalm 100:2)

Delight yourself in the Lord (Psalm 37:4)

Christ endured the cross for the joy set before Him (Hebrews 12:2)

The Apostle Paul was sorrowful yet always rejoicing (2 Cor. 6:10)

Rejoice in the Lord always (Phil. 4:4)

To the degree that you share in the sufferings of Christ, keep on rejoicing (1 Peter 4:14)