Without a heart of joy and celebration all the other disciplines eventually erode into boring and ritualistic burdens at best, and such "practicing" Christians become nothing more than modern day Pharisees.
Outside the transformed life found only in Jesus Christ and a life walked in step with His Spirit, there is absolutely no joy. No one has more reason to celebrate than a Christian. We should be elebrating both in good times and when our lives look like a tragedy. We know this doesn't mean to swallow all other human emotion. It's not our goal to be empty plastic people who rejoice in evil done to us.
The joy of the risen Christ in us and the reality of His presence result in joy that outweighs any temporary sorrow. Joy can be expressed in any situation if we trust that on the other end of it are all the sure promises of God and a closer walk with Him. A parent knows that their teenager will eventually let lose of their naïve superiority complex because every parent was also once a teenager and knows it will pass. A woman in labor forgets her pain, overcome with the mystery and beauty of a child that bears her image. Even in the midst of suffering we can feel God very close, expressed in absurdly visible exuberance. He has done it before, so we remember and trust He will continue to deliver us.

