This quote is from C. S. Lewis in his book, Letters to Malcolm: Chiefly on Prayer:

I do not think that the life of Heaven bears any analogy to play or dance in respect of frivolity. I do think that while we are in this ‘valley of tears,’ cursed with labour, hemmed round with necessities, tripped up with frustrations, doomed to perpetual plannings, puzzlings, and anxieties, certain qualities that must belong to the celestial condition have no chance to get through, can project no image of themselves, except in activities which, for us here and now, are frivolous.

For surely we must suppose the life of the blessed to be an end in itself, indeed The End: to be utterly spontaneous; to be the complete reconciliation of boundless freedom with order–with the most delicately adjusted, supple, intricate, and beautiful order?

How can you find any image of this in the ‘serious’ activities either of our natural or of our (present) spiritual life? Either in our precarious and heart-broken affections or in the Way which is always, in some degree, a via crucis?

No, Malcolm. It is only in our ‘hours-off,’ only in our moments of permitted festivity, that we find an analogy. Dance and game are frivolous, unimportant down here; for ‘down here’ is not their natural place. Here, they are a moment’s rest from the life we were place here to live.

But in this world everything is upside down. That which , if it could be prolonged here, would be a truancy, is likest that which in a better country is the End of ends. Joy is the serious business of Heaven.

– C.S. Lewis, Letters to Malcolm: Chiefly on Prayer (San Diego: Harvest, 1964), 92-93.