The people in the story had every reason to be filled with sorrow because of their sin, a sorrow that would lead them to repentance. And that would necessarily follow. But before that, the Lord knew these people needed to experience joy over him. And surely something of his joy, themselves.
At the core of our existence there needs to be a reverential awe as well as awe-struck wonder in God. “The fear of the Lord is the beginning of wisdom.” And the revelation that comes to us in Jesus is one of love: God’s love for us and for the world. It is not merely intellectual, but something to be experienced by the Spirit. Of course it is in and through the cross, Jesus’ death, that God’s love is made known. God is not wanting humans to cower in his presence, though that is necessarily so when they are judged because of their wickedness. In Christ by his death God takes on himself our judgment and reveals himself as the God of consummate love and never ending beauty. And again this is not just like appreciating a great work of beautiful art. It is somehow being included ourselves, so that we can begin to experience something of the beauty of the Lord. Our sins being forgiven, so as now to be included among God’s people in God’s presence in which there is fullness of joy.
The joy of the Lord and sorrow are not necessarily mutually exclusive. In a sense they are not at all. Even in the deepest sorrow, the joy of the Lord is present, yes even in those depths, though we likely are not thinking of that at the time. It is a grace to weep in this world, borne by the joy of the Lord. The two can go hand in hand. In the case of the passage quoted above in Nehemiah, the people were beginning to develop a healthy sorrow over their sin, as scripture was read. Such conviction of sin is a companion with the joy of the Lord. Paradoxically we experience joy over the Lord, and the Lord’s joy as we have proper conviction over our own sins, and even as we share in the sorrows and suffering of Christ in this world.