When trying to explain the Catholic understanding of sexuality to someone "outside", I almost invariably find myself falling back on analogies relating to diet and gluttony. It's a natural comparison, and while modern society has lost any sense that it's reasonable to have any less sex if you want to have fewer children, people are able to get more righteous then ever over the point that if you want to be fit you must, must, must eat moderately and exercise more.
Indeed, diet and exercise may be the one thing relating to sexuality where modern culture understands a great deal of self denial. After all, one of the motivations for all this diet and exercise is, I think one may honestly admit, to look better while naked.
Which leaves the obvious question: Why has a Church which finds itself swimming against a quickening current in regards to its teaching on birth control nearly totally abandoned any sort of severity in regards to fasting?
Sure, we're an "Easter people" and all that, but maybe some rigorous self denial for the sake of religion would help us with some rigorous self denial for the sake of our faith. I've been pretty much as bad as the next fellow on this -- doing the mental calculation of whether I can make one more cup of coffee and still make the hour fast before mass or falling to the "I'll say some extra prayers tonight as a sacrifice instead" temptation on Fridays outside of Lent when meat is all that appears on the menu. But this is, after all, part of the problem. The constant NFP lament is "Look, we played by the rules all those years before we were married. Why does there have to be frustration now too?"
If virtue is a habit, perhaps it's time to form some more habits around denial of appetite.