The differences between happiness and joy

Today my pastor preached a message about joy. And it really got me thinking about the differences between joy and happiness. What are they? And how exactly are they different? Well you might as well settle on down because I am about to give you a glimpse into the ramblings of my mind as I sort out the answers to these questions in my head. And yes, this is all thought up as I go along. Feel free to grab some popcorn...I would. (don't worry, I'll wait for you) :)
Now if it is all popped and ready, (and hopefully just a mite burned because it tastes better that way,) I am going to start off with a statement of belief. I believe that while happiness is just a feeling, joy is a state of mind. Now comes the explanation: I once heard a saying that went like this; "Happiness is a choice." I really liked it at the time. I thought it had a good message - that we should choose always to be happy. But then I stumbled upon a problem. I had talked to a friend of mine on the phone. She wasn't doing so good. She said she was tired of pretending to be happy all the time..when she really wasn't. I was stumped. Where, I wondered, was the dividing line between choosing everyday to be happy, and just pretending to be?
Well I am happy to say that I finally think I have figured that out. You wanna know the answer? It's simply this; the difference between happiness and joy. Explanation? Joy is really the choice, happiness is just an emotion that comes and goes. What I really want you to understand is what joy is, exactly. Let me give you an example. Have you ever read the book Pollyanna? If you haven't I suggest you do so. It's not exactly the greatest book ever written, and it's pretty slow at parts, but it has an amazing message. It's about a little orphan girl who goes to live with her (not exceptionally very nice) Aunt Polly. This girl has had a tough life, it seems that everything has gone wrong for her, but amazingly, through it all, she is glad. She remembers back when her father was alive and they used to read the scriptures about gladness. They counted the verses together and found so many times that God said to be glad and rejoice that they came up with the glad game. The way you play is to simply find something to be glad about in every situation. Like, for instance, when Pollyanna was hoping so bad for a doll to come in the missionary barrels that came for the orphans, but the only thing that showed up was an old pair of crutches. She found that she could be glad simply because of the fact she didn't need the crutches. And this is a perfect example of choosing to have joy in any and every situation; whether good or bad.
Really though, gladness, joy, and happiness are all just names. Labels, that we have assigned to different feelings, choices, and emotions. It doesn't matter particularly which one you assign to another, but that you understand the things you are assigning them to. It is simply this; I understand happiness to be an emotion that comes and goes, and joy to be a choice we make every day. To choose to rejoice in the Lord always, and again I say rejoice!