St. Augustine said,
"Let us sing alleluia here on earth, while we still live in anxiety, so that we may sing it one day in heaven in full security.... We shall have no enemies in heaven, we shall never lose a friend.
God's praises are sung both there and here, but here they are sung in anxiety, there in security; here they are sung by those destined to die, there by those destined to live forever;
here they are sung in hope, there in hope's fulfillment;
here they are sung by wayfarers, there, by those living in their own country.
So then.... let us sing now, not in order to enjoy a life of leisure, but in order to lighten our labors. You should sing as wayfarers do -- sing, but continue your journey ... Sing then, but keep going."