I don't appreciate being told how to feel. Paul comes dangerously close in telling his readers and hearers to express joy. I also don't appreciate a Pollyanna attitude toward adversity in life. From where does Paul's joy come? It is precisely in his imprisonment that he finds his co-workers in Christ respond in the most powerful ways. Despite the miserable condition of a prison sentence, Paul looks to the response of a community of faith moved by the Gospel, not some misplaced set of feelings.
After the deaths at Sandy Hook School in Connecticut a few days ago, rejoicing seems out of place. However, Paul's example tells us that it is not mere emotional fortitude and will that move us to a better place, but the love of God at work in others. Fred Rogers' mother told Fred to look to the helpers to find grace. It is that kind of passion reflected in the unjust death that Christ suffered that transformed the world and freed us to be that kind of presence in the world.