"The same Creator, Who in His bounty and wisdom willed to make use of the work of man and woman, by uniting them in matrimony, for the preservation and propagation of the human race, has also decreed that in this function the parties should experience pleasure and happiness of body and spirit. Husband and wife, therefore, by seeking and enjoying this pleasure do no wrong whatever. They accept what the Creator has destined for them."
"Nevertheless, here also, husband and wife must know how to keep themselves within the limits of a just moderation. As with the pleasure of food and drink so with the sexual they must not abandon themselves without restraint to the impulses of the senses. The right rule is this: the use of the natural procreative disposition is morally lawful in matrimony only, in the service of and in accordance with the ends of marriage itself. Hence it follows that only in marriage with the observing of this rule is the desire and fruition of this pleasure and of this satisfaction lawful. For the pleasure is subordinate to the law of the action whence it derives, and not vice versa—the action to the law of pleasure. And this law, so very reasonable, concerns not only the substance but also the circumstances of the action, so that, even when the substance of the act remains morally safe, it is possible to sin in the way it is performed."
Sex is good. What follows is a lengthy rejection of hedonism. Here's the punchline.
"There are some who would allege that happiness in marriage is in direct proportion to the reciprocal enjoyment in conjugal relations. It is not so: indeed, happiness in marriage is in direct proportion to the mutual respect of the partners, even in their intimate relations; not that they regard as immoral and refuse what nature offers and what the Creator has given, but because this respect, and the mutual esteem which it produces, is one of the strongest elements of a pure love, and for this reason all the more tender."
That's Pius' answer to those whose worry about "sexual compatibility" in marriage and avoid or end marriage for lack of it. Marital happiness is dependent on love and respect between spouses, not the frequency and quality of orgasms.
"This teaching of Ours has nothing to do with Manichaeism and Jansenism, as some would have people believe in order to justify themselves. It is only a defense of the honor of Christian matrimony and of the personal dignity of the married couple."
Just in case you were afraid the pope's teachings were based on heretical views of the body and sexuality, he assures us they aren't. 😉