Joy is different from happiness. Happiness comes from good times when something good happens to you. Joy comes from God regardless of what the circumstances are. God gives us abundant joy when we trust in Him. We aren't worrying about will happen tomorrow, we know all of the beautiful things that are coming, and we know we are loved. Happiness isn't bad, I love to feel happy when things are going good. But your happiness in your good times should be added onto the joy you have all the time. Happiness is something that comes and goes and you can't control, you aren't going to be happy when someone you love dies you just aren't. However you can still have joy in that situation because you know they're with God even though it feels like your heart is being ripped up since you miss them. It isn't easy to find joy in every circumstance you have to trust that God is working things out for your good and that He has a plan. When you put your trust in Him you can be full of His abundant joy all of the time no matter what happens.