More from John Ortbergs 'The Life You've Always Wanted' (the rumour is that planned follow up volumes include one for single men: The Wife You've Always Wanted, and for failed bakers: The Loaf You've Always Wanted. My apologies.)
In a chapter on the spiritual discipline of joy, he cites Dallas Willard:
"Failure to attain a deeply satisfying life always has the effect of making sinful actions seem good...normally our success in overcoming temptation will be easier if we are basically happy. To cut off the joys and pleasures associated with our bodily life and social existance as 'unspiritual' can actaully have the effect of weakening us in our efforts to do what is right."
In other words, joy is the best antidote to sin, because the more fun we are having, the less we'll be attracted to sinning.
He also quotes a beautiful passage from Chesterton, also used in this cracking sermon on how to be childlike by Tony Campolo :
Because children have abounding vitality, because they are in spirit fierce and free, therefore they want things repeated and unchanged. They always say, "Do it again"; and the grown-up person does it again until he is nearly dead. For grown-up people are not strong enough to exult in monotony. But perhaps God is strong enough... It is possible that God says every morning, "Do it again," to the sun; and every evening, "Do it again," to the moon. It may not be automatic necessity that makes all daisies alike: it may be that God makes every daisy separately, but has never got tired of making them. It may be that He has the eternal appetite of infancy; for we have sinned and grown old, and our Father is younger than we.