We celebrate what brings us joy. Because our joy is based on God—who He is, what He is doing, and what He has promised to do—we should celebrate deeply and often.
Joy has always been at the very heart of the triune God. As C.S. Lewis wrote, "Joy is the serious business of heaven."
We need more joy in our world. More wonder. More awe. More marveling. And the people of God should be the bringers of these things. The joy-bringers, the party people. How can we not be? Look at all we have to celebrate! Look at Who we are invited to celebrate!