Once it became clear that the Second Coming would not be immediate, and that most people had to do the Martha thing and live in the world, with all the messy challenges and demands the world makes on us, then some code of Christian conduct had to be put forward for the two things that were incumbent upon every knight, and indeed upon every person - loving and fighting: for we all do both in one way or another every day.
In other words, "libido", or lust-for-life always involves loving and fighting, and there are two extremes of conduct when it comes to either. Those two extremes are disengagement and indulgence.
Disengagement is explained by Our Lord in the Parable of the Talents, when the cowardly steward buries his lord's talent in a hole so as to avoid any chance of loss. This is condemned, for our light is to be put on a hill, not covered with a basket. Our Lord gives us our talents so as to engage them in life and put them at risk. This can be done whether one leads a contemplative or an active life, and the sin of not doing so can be committed by anyone, in religious endeavors, in secular endeavors, and in sex. Indeed, in the sexual realm, one of the worst things about contraception, masturbation and sodomy is that these activities deliberately bury or squander something in a place where we know it will do no good. Sterile sex plays it safe, and our talent - our libido - was not meant for this. The risk of loss and pain and the dizzying thrill of the new life and unpredictability that true engagement leads to - these things scare us. But we are not to hoard, hold back or bury.
And yet neither are we to indulge, for indulgence is the opposite pole. Desire can easily turn to lust and righteous anger can easily turn to wrath. Lovers can ravish and soldiers can slaughter.
Only in the fullness of Christian culture are we taught the delicate balance between the two, and Chivalry is one way we used to be taught that, even the secular form of chivalry, which was the Christian code that boys should be courteous to girls - both because we should protect the innocent and weak and also because we love them and want to make babies with them - fighting and sex were thus managed with the leash of sacrifice and surrender that comes with the Cross.
And, believe it or not, I think Shakespeare wrote a whole play on this subject - one of his lighter comedies.
For more on how Much Ado about Nothing is really Much Ado about Something, read my article on The Christian Shakespeare here (originally published in the St. Austin Review, a magazine you should all subscribe to).