Joy in Christians

I have been thinking about what to preach on when I go to Fort Bragg next Sunday. Karen suggested something on joy, like from a sermon series I did on Philippians 4--"How to have joy".
It is interesting that I came across this article from Preaching Today about the joy that Christians have. I will give you a few excerpts:
...our preacher shared an interaction he'd had with a supermarket clerk. As she checked each of his items, she stopped to look him in the eye and say, "We always know when your church lets out on a Sunday—saddest, meanest group we deal with all week long." I look back on the state of our church and wonder how our attitudes were affecting the children of the congregation. The Sunday School teacher probably stood before the class each week, singing, "If you're happy and you know it, clap your hands," only to be met by a dreadful stretch of silence. But who could blame the kids for not even flinching at the invitation? Their little, peering eyes had been on a downcast mom and dad all week! We held fast in our hearts to the Good News, but joy—even that wonderful state of happiness that joy often brings about—seemed just beyond us. At the beginning of "A Christian's Happiness," Timothy Keller confesses that even as a Christ follower, he often struggles with issues of joy and a more consistent state of happiness. So it pleases him to no end that Paul's words in Romans 8:28–30 show a pathway toward a more impervious, relentless joy.

And then a sermon illustration that I might use in my message:
America Is World's Saddest Nation
According to a recent study by the World Health Organization and Harvard Medical School, America may very well be the saddest nation in the world. Researchers found that 9.6 percent of Americans suffer from depression or bipolar disorder—the highest among 14 major nations polled. Those nations that scored better than the U.S. suffer from ongoing wars and rumors of war (Lebanon), vast unemployment (Mexico), and profound poverty (Nigeria). In his Wall Street Journal article, "The Great Depression," Bret Stephens argues that perhaps America scores poorly as a nation because its population is generally comfortable and wealthy. Such luxuries allow more time for critically picking apart life situations and personal circumstances. Those who live in countries torn apart by varying social and economic issues have less time to fret over personal gain and ambition. They are simply too busy trying to survive. So what could turn our sad nation around? The research shows that the citizens of the world's happier nations find a steady source of joy in their families, their religion, and their traditions. —Brian Lowery, associate editor, PreachingToday.com; source: Bret Stephens, "The Great Depression," The Wall Street Journal (3-9-07)

How is YOUR joy?