Several years ago, when I was first introduced to the Theology of the Body, I heard that married love needed to be free, total, faithful, and fruitful. (I know Christopher West has brought it up in a number of different talks.) It made sense to me, but I honestly didn't know where it came from, exactly.
My current thought is.... Humanae Vitae. Yeppers, and I only had to read it twice (okay, maybe three times) to pick up on it.
It is free, "not...merely a question of natural instinct or emotional drive. It is also, and above all, an act of free will, whose trust is such that it is meant not only to survive the joys and sorrows of daily life, but also to grow, so that husband and wife become in a way one heart and one soul, and together attain their human fulfillment." (Humanae Vitae, 9)
It is total, husband and wife generously share everything. "Whoever really loves their partner loves not only for what he receives, but loves that partner for the partner's own sake, content to be able to enrich the other with the gift of himself." (Humanae Vitae, 9)
It is "faithful and exclusive of all others, until death... Though this fidelity of husband and wife sometimes presents difficulties, no one has the right to assert that it is impossible; it is, on the contrary, always honorable and meritorious. The example of countless married couples proves not only that fidelity is in accord with the nature of marriage, but also that it is the source of profound and enduring happiness." (Humanae Vitae, 9)
It is fruitful. "Marriage and conjugal love are by their nature ordained toward the procreation and education of children. Children are really the supreme gift of marriage and contribute in the highest degree to their parents' welfare." (Second Vatican Council, Pastoral Constitution on the Church in the World of Today, no. 50: AAS 58 (1966), 1070-1072 [TPS XI, 292-293].*)
For me, so many of the romantic scenes in movies and TV fall short right now. It's usually about someone being overcome with passion (i.e. lust) or feelings for someone else. I don't know if you've noticed, but many, many times, they are already in a relationship with someone else (sometimes dating, sometimes engaged or married) but the message is that the new love is right and cannot be denied. As a single person, if I ever get married, that's not the kind of relationship I want. I want someone who has decided to make it an act of free will to love me, and is not only ruled by natural instinct or emotional drive. I would like to give myself totally to him and receive the totality of who he is. I want to know that we are both committed to be faithful. Not because it's easy, but because it's right. To me, a marriage that is free, total, and faithful, will also be fruitful. Unfortunately, not always with children (due to high numbers of infertility), but by the nature of it's existence and witness to the world, that kind of marriage will bear fruit.
To me, it is hard to even write about these characteristics of marriage separately. How do you separate one of these from the other? Try to explain giving yourself freely without giving yourself totally. Or how are you truly faithful until death, without a supreme act of free will and trust? Perhaps in this society it's harder to see how openness to new life fits into this, but for me, it is equally a part of the whole equation. You cannot give yourself totally, except your fertility. To give totally is to give all. And so forth.
So many people want to take the "rules" out of marriage and love so that we will be free to do whatever seems good at the time. However, when you strip away these different aspects so that they no longer have to exist, then the type of love that I am looking for no longer exists.
*Ha! You thought it was going to be paragraph 9 of Humanae Vitae again, didn't you? Well, it was from that paragraph, but it was a quote from 2nd VC, so I cut the middle man.