In relationships, we often think of what we need to give in order to get what we want, whether it’s exchanging affection for sex, financial support for companionship, or some other quid pro quo. This mindset may be appropriate when searching for a partner, and even throughout a short-term relationship, but not during a relationship that you want to go the distance, because it represents too much of a perspective from “me” instead of “us.” This kind of exchange works for market transactions, in which respect is owed but care is not expected, but not relationships built on respect and care.
This is the natural approach to take while searching for someone to form a relationship with. After all, before you find somebody, you’re only looking out for yourself. You have an idea what you have to offer to another person, and you also have an idea what you want from him or her. Through meeting and talking to people, you learn which people have what you want and want what you have. And even as a relationship is beginning and developing, it is natural to “look out for yourself,” since you’re still getting to know this person. But as the relationship develops, and you and your partner begin to satisfy each other’s needs without thinking about it, thinking about it what you’re “getting out of it” only gets in the way. (Yet another example of wei wu wei, or "action without action," in relationships.)
Exchange in committed relationships may sound a lot like market exchange, but it is more difficult, even in practical terms. In the marketplace, rudimentary forms of money developed mainly to solve a particular problem: the double coincidence of wants. Here’s an example: in a world without money, if I make furniture but I need eggs, I have to hope the farmer selling eggs wants my furniture so we can barter. If not, I have to find out what the farmer needs—say it’s clothes—and hope the tailor making the clothes the farmer wants also wants my eggs. But if the tailor needs bread, then I go to the baker and… well, you get the idea. Money solves this problem by offering a common medium of exchange. I can sell my furniture to whomever wants it, receive money in exchange, and use that money to buy eggs—and the farmer can use the money to buy clothes, and so on.
This doesn’t work in the “mating market” because the point is usually to get most of the things you need from the same person who wants what you have to offer. (This is somewhat easier in polyamorous relationships, but even then, ideally, each person’s needs would be met within the group.) Certainly we shouldn’t depend on our romantic partners for everything we need in life, but we would like the lion’s share of it from them—and we expect them to get much of what they need from us. When we don’t get certain important things, such as emotional or physical intimacy, we are tempted to stray. People may claim that they get their physical needs satisfied elsewhere so they can be more emotionally generous with their partners—like selling eggs to the tailor to get clothes to buy furniture—but this misses the point of a committed relationship. (The difficulty of getting most of what you need from one person, of course, is one argument often made for polyamorous relationships.)
We can still want things out of our relationship, of course, and so can our partners—how could we not? But to “bargain” for them reduces love to convenience. There’s nothing wrong with saying you’ll wash the dishes tonight if your partner does them tomorrow, but trading sex for affection (or the other way around) is different. Ultimately, this is related to compromise—as I wrote in a previous post, it's fine to compromise on the little things but not on those which make up who you are—and the same goes for “exchange.” Never give up the things that make you you, and never put a “price” on them. When you do, either to satisfy your partner’s requests or in order to make your own, that may be a sign that the relationship is weakening, because you and your partner are thinking less in terms of “we” and more in terms of “me.” If you find yourself thinking this way a lot, it may be time to consider ending the relationship, which you can only do from your own point of view (as described in this post).
In relationships, there is a time to think of yourself—such as the beginning or ending of a relationship—but in between, if you want the relationship to last, you should find yourself (and your partner) thinking in terms of "us" rather than "me" and "you." Doing things for each other should come naturally, not strategically. As I wrote here in regard to using game theory to model behavior in relationships, strategic thinking is for asking for a promotion or buying a car—not for maintaining a relationship. You and your partners are not self-interested negotiators, but rather a team, and there's no... well, you know.