Joy is the serious business of heaven.

Psalm 66:8-12 
8  Bless our God, O peoples; let the sound of his praise be heard, 9 who has kept our soul among the living and has not let our feet slip. 10 For you, O God, have tested us; you have tried us as silver is tried. 11 You brought us into the net; you laid a crushing burden on our backs; 12 you let men ride over our heads; we went through fire and through water; yet you have brought us out to a place of abundance.