I first heard about the Theology of the Body (TOB) a few years back during my early conversion to Catholicism. Wonderful stuff. I still think so, although I have some misgivings about its emphasis and reception.
I was talking to one of my friends about it last night and he pointed out that John Paul II (JPII) was known for emphasizing the positive. In an age when the image of sex had been turned on its head by the Sexual Revolution, perhaps JPII was trying to do some marketing. Making the sexual teachings of the Church appear beautiful and desirable to a modern mentality is a tall order. TOB is really the ideal avenue for this kind of marketing. It presents the Truth of the Catholic faith and leaves a passion for pursuing this ideal.
But, as I was saying last night to my pal, I long for the days when the saints of the Church regarded sex as something dirty and troublesome. In a meditation designed to remind readers of their humility, St. Bernard encourages them to remember the nature of their origin; namely that they were created through the sexual act. My friend pointed out Augustine's assertion that the marital act always contained some venial sin. To this day, the married priests of the Orthodox churches of the East abstain from sex before the celebration of the Holy Mysteries.
I think TOB can give an idealized vision of human sexuality that doesn't prepare couples for the vicissitudes of the reality. Surviving these vicissitudes takes more than an intellectual grasp of an ethos like TOB. It requires character, which is built slowly over time. I suppose TOB can be the door, but living in the reality of a human sexual relationship is another road entirely. And the terrain of this road isn't discussed very often.