Happiness is conditional, joy is not. Joy comes from the realization that you are a child of God. You are able to be thankful in the good times and the bad. The good times are a gift for your enjoyment and the hard times are gifts for our sanctification. Joy is being content as you walk in the spirit and reject the temptations and deeds of the flesh. It is the satisfaction of having God and at the same time pursuing Him into the richness and righteousness of the Holy Spirit. (James 5:13) Is anyone among you suffering? Let him pray. Is anyone cheerful? Let him sing praise. Joy is found when are eyes are always on God.