Christian joy is not a giddy, superficial happiness that can be devastated by illness, economic difficulties, broken relationships, or the countless other vicissitudes and disappointments of life. Instead, it flows from the deep, unshakable confidence that God is eternally in control of every aspect of life for the good of His beloved children – a confidence rooted in the knowledge of His Word. God’s character, the saving work of Christ, the sanctifying work of the Holy Spirit, divine providence, spiritual blessings, the promise of future glory, answered prayer and Christian fellowship all cause the believer to rejoice.
John MacArthur