Joy that is a fruit of God's Spirit has its roots in the realization of God's purpose and its outworking that transforms us into His image. Biblical joy begins when God calls, and we hear the gospel, understand, and believe it.
Biblical joy is bound up in our relationship with Him and our understanding of what is happening to our minds. We walk to the beat of a different drummer than this world because we understand God's overall purpose. We know we have been forgiven and have a place in His purpose because we now have His Spirit. No more life-changing experience can ever happen to a human than when God calls and understanding dawns. It forever alters our perspective on life itself and on the things we formerly trusted to give us satisfaction.
Henceforth our joys must arise from yielding to fulfill God's great creative purpose and seeing it accomplished. This is why we were born! Because of this, we can look forward to hearing Him say:
Well done, good and faithful servant; you were faithful over a few things, I will make you ruler over many things. Enter into the joy of your lord. (Matthew 25:21)