This is an old talk from John Piper:
Commandments on Joy.
We are commanded to be happy Psalm 100
We are threatened terrible things by God, if you are not happy in God. Deut. 28:47
The nature of evil requires the purest Joy. Jer 2.12
The nature of Conversion requires that we pursue Joy in God: Matt. 13.34
The call to self denial is the call to the pursuit of joy. Mk. 8:34-35
You cant love people if you cant pursue your own Joy: Acts: 20:34 (When it is hard to do something we must love with the hope of Joy)
Pursuing your own Joy glorifies God. When you delight in God, He is made much of. Pursue your joy in Christ so deeply that you cant shake the joy off of you.