Psychologically, we feel attached to the person we have sex with. "Liberal" people think this is childish and something to be outgrown from in order to do it just like friends have drinks. It is not. It is what sex is meant to be: something that makes us feel closer to our partner. To "outgrow" this feeling, is the same as to "outgrow" the sensation of pain when we touch fire or the sensation of pleasure when feeling the wind blow on a sunny summer morning.
No offense, but this feeling of attachment you are mentioning seems to actually have been responsible for some of the worst atrocities in history, and is actually very animalistic in nature. It's about selfishness and the evolutionary desire to pass on your genes "I want to be the one to pass on my genes", "I want to be the one with the mates", "I want to own you", "You are MINE and I want you to only have sex with me".
Nobody knew about genes until the 20th century. People *never* thought of sex in terms of passing genes. At most they would think of their "names", keeping such and such property in the family, but definetly nothing of modern pseudo-biological rationalizations.
James, I would suggest you take a more existential approach to life. What is it that you experience when in this kind of situation? Do you really feel you want to pass your genes? Or it is simply the attachment? Never in my life, even when it was the basest of feelings I thought in genetic terms. In fact, most of the time people actively try to avoid having any babies in the process, some even getting to the point of killing their children in the womb.
You are right that that love can be corrupted and become possessive. Just like reason can become cold and psychopathic, peace can become apathy, faith can become idolatry, discernment can become self-righteousness and so on. Also, the feeling of attachment we have in and after sex is not spousal love itself, but it is meant to reinforce it. And of course it is a sacred thing:
15 Do you not know that your bodies are members of Christ himself? Shall I then take the members of Christ and unite them with a prostitute? Never! 16 Do you not know that he who unites himself with a prostitute is one with her in body? For it is said, “The two will become one flesh.” 17 But whoever is united with the Lord is one with him in spirit. 18 Flee from sexual immorality. All other sins a person commits are outside the body, but whoever sins sexually, sins against their own body. 19 Do you not know that your bodies are temples of the Holy Spirit, who is in you, whom you have received from God? You are not your own; you were bought at a price. Therefore honor God with your bodies. (1 Cor. 6:19-20)
See the warning? We are one body with every single person with whom we have had sex with in our lives and that remains so unless we have repented. And God does not unite Himself with such amorphic non-individuals. We must repent of every single intercourse with every single person that is not our wife/husband, even if done before marriage with consent. Each of those acts was an aggression to ourselves, to the other person, to our spouse and to God.
Our bodies don’t stop being the temples of the Holy Spirit during the sexual intercourse. And not only that, God’s very act of creating a soul may be materialized out of this act. And we are – or should be - undressing not only our bodies, but our very hearts before our spouse, letting the nakedness of the body be an icon of how we put ourselves before our spouses: without masks, clothes, in fragility, being vulnerable to the other out of love. In the Philokalia nakedness is classified as a *virtue*. Adam and Eve were created naked because “God saw it was good”. And in that nakedness we proceed to a whole “ritual” of tenderness, of exchange of affection and pleasure that, despite any belief, is an icon of the union of God and the Church as seen in Canticle of Canticles.
Now, of course, we don’t live sex in that way. It is used as just one more toy to play with, even among spouses. But the way people live and use it is not what God meant it for. Surely, sex is necessary only as a provision for this fallen world. But that does not prevent God from sanctifying it, just like He sanctifies other such provisions as food, shelter and so on. What we do with our bodies and hearts in these promiscuous fornications we live (and I include even heterosexual serial monogamy - of which I am guilty too - rationalized as “necessary experiments to find out the ‘right’ person”) is exactly what we see in Daniel 5 (http://www.biblegateway.com/passage/?search=Daniel%205&version=NIV
), a profanation of the Temple of God, an abomination put in the innermost altar of the temple, misusing that which is meant for God for mundane blasphemous frivolity. God have mercy on me for that, sin over sin! Not only do we profane the temple of the Holy Spirit and use its chalices for debauchery, we do that in the name of using our sisters (or brothers in the case of girls) as “experiments” depriving them and us of the proper dignity of our personhood. That is why like a temple, it must be dedicated first in marriage, and be one and just one.
18 May your fountain be blessed,
and may you rejoice in the wife of your youth.
19 A loving doe, a graceful deer—
may her breasts satisfy you always,
may you ever be intoxicated with her love.
13 Another thing you do: You flood the Lord’s altar with tears. You weep and wail because he no longer looks with favor on your offerings or accepts them with pleasure from your hands. 14 You ask, “Why?” It is because the Lord is the witness between you and the wife of your youth. You have been unfaithful to her, though she is your partner, the wife of your marriage covenant.
15 Has not the one God made you? You belong to him in body and spirit. And what does the one God seek? Godly offspring.[a] So be on your guard, and do not be unfaithful to the wife of your youth.
16 “The man who hates and divorces his wife,” says the Lord, the God of Israel, “does violence to the one he should protect,” says the Lord Almighty.
So be on your guard, and do not be unfaithful.
We mustn’t, of course, go to the radical opposite and make our bodies or sex more than sacred and an idol in itself. There are indeed people for whom sex is the “alpha and omega” of their lives, the core of their self-identity, the activity in which they have a sense of self-realization. That is idolatry if not outright a disease.