Joy is a very tricky thing when you actually think about it, especially when you compare it with happiness. There are a number of ways to think about the two but the best comparison I’ve come up with so far is: happiness is a result of circumstance while Joy is an inward reality independent of circumstance. To put it another way, things, occurrences, events, etc. make you happy. For example, receiving a gift makes you happy, the relative who lives far away coming for a visit makes you happy, your sports team winning makes you happy (not every happy-making thing is big and significant). Joy on the other hand is a deeper, more settled part of who you are. It is possible to be joyful and unhappy at the same time.
I did a quick and very unscientific survey of “happiness” and “joy” in the New Revised Standard Version. Happiness occurs 7 times; Joy occurs 267 times . . . not definitive but might be considered suggestive as to which is more important in the Bible.
No matter where you find yourself in this discussion, I hope one or both of these sermons will be helpful to you in this season of Advent as you move into the season of Christmas.