The two are not the same. Indeed, we are commanded to rejoice, but we are not commanded to be happy. Happiness is an emotional, temporary feeling due to circumstances around us. Joy is that deep inner “peace that passes understanding” (Philippians 4:7) which only those who are the children of God can truly claim. That is why God’s children can have joy even when it is the darkest night, even when the surrounding circumstances beat us down and engulf us. In John 16:33, our Lord Jesus told us, “Be of good cheer, for I have overcome the world.” With a promise like that, how can God’s children not be joyful, even when they cannot be happy?