1 Thessalonians 1:6
King James Version (KJV)
6And ye became followers of us, and of the Lord, having received the word in much affliction, with joy of the Holy Ghost.
Joy is a benefit of being a follower of Christ. Joy is not the same thing as 'happiness,' for joy is not dependent on circumstances. Rather, a person can be filled with overflowing joy even in the midst of severe suffering. It may seem contradictory or impossible, but those who belong to the Lord know exactly what I mean.
While happiness is fleeting, ebbing away when troubles comes, joy on the other hand is an inner knowledge that with God all is well, that we are kept in His care, and that in His will we are part of the greatest work that could ever be accomplished on earth. His presence alone fills our hearts with assurance, comfort, and yes, joy, no matter what the circumstances.
This does not mean we never get worried or that we are never troubled within. Those things are the natural human response to trouble. But joy comes in our hearts and minds when we realize that the God of all the universe dwells within and that with Him we are secure.
Praise the Lord.
Song: Ernie Haas and the Signature Sound Quartet sings 'Happy Rhythm.'