To begin, Paul never said we would always be happy, but he did say we should always rejoice. How do we reconcile these two things? It begins with understanding the words Paul used in verse 16. The word “rejoice” does not mean the same thing as the word “happy.” Happiness is often predicated upon what "happens" to us, while rejoicing, as Paul used the word here, refers to Christ in us, the hope of glory (Co 1:27).
Beware! But Be Glad (Pentecost Sunday)
We are covenant people, not because of the externals, but because God, through the Holy Spirit, transforms our hearts and draws us into a powerful relationship with Himself that lights a fire in us that makes us a light to the world; a city on a hill that cannot be hidden; and salt with savor as living witnesses of Jesus our Savior.