Christian joy has nothing to do with material blessings or smiles and euphemisms plastered across the inevitable, unavoidable, natural sorrows of life. Having Christian joy doesn’t mean not having depression, or not being sad, or not struggling.
Christian joy isembracing that suffering because Christ has made suffering redemptive. It’s uniting yourself with Christ on the cross and praying that you pass through your suffering, tempered like metal in fire, to become a stronger, better, more loving person. It’s being able to see through the struggle to Christ who is your bedrock, who will always take care of you. Christian joy is not about external circumstances or superficial emotion. It’s a state of being united with Christ in trust that is stronger than fear.
True, there are too few living Christians today who exemplify that. This is an age short on living saints. But it’s equally true that non-Christians look at Christians who are doing their daily best to become saints and sneer, “That doesn’t look very ‘joyful’ tome.”
"Joy" to the world today means “happiness." “Happiness" to the world today means “feeling pleasant." By that definition, no one of any creed or philosophy will ever attain complete happiness on earth. It’s impossible. Happiness to the Christian is knowing the truth—Christ—and living in Him. That kind of happiness, of joy, is the seed of completenes, because it alone is unchanging in any circumstances—indeed it enables you to survive whatever circumstances. And eventually, that joy alone is able to carry you into into an eternity where the fulfillment of complete joy is possible.
That’s why it’s so important that Christians actually, actively, visibly bring Christ into every aspect of their lives. It’s too easy for onlookers to write off the discernibly Christian elements as “not joyful/happy” and/or attribute any apparent happiness in the Christian’s life to whatever cause suits their preconceived ideas.