"Rationality" -- or, really, just a thoughtful attitude -- has some major advantages in relationships, I've found. Some important relationship skills that require rationality:

• Being able to consider hypotheticals without bumping into ugh fields.

"If I ever cheated on you -- not that I would -- I would use a condom." You need a rational person to say this, and a rational person to hear it. An irrational person would never want to consider the possibility of cheating, and so wouldn't want to think of contingency plans; such a person might be offended by the very suggestion that a bad situation might happen. In the same vein, rational couples can discuss things like "if my business fails," "if we break up," "if this crazy feeling of limerence fades," and so on. You can't deal with bad contingencies well if you can't think about them or discuss them at all.

• Being able to suspend the Typical Mind Fallacy.

People are different. Something could matter a lot to your partner that doesn't matter at all to you. Or vice versa. You can make each other happier if you can put effort into the things that the other person is passionate about even when you can't imagine feeling that way yourself. This is also a great way to diffuse fights before they even start; before you assume your partner has a nasty thought or attitude, find out what he's actually thinking. It can be surprising.

• Learning from experience.

It's a rationalist skill just to be able to notice what your significant other does and predict that he'll keep doing it. So many relationship problems stem from the failure to notice patterns. Notice a behavioral pattern and you can learn to trust someone, learn his strengths and weaknesses, or learn to do what consistently makes him happier.

• Understanding that statistics predict but don't control our behavior.

Some stereotypes are roughly true in a statistical sense -- people like high status and attractiveness in their mates, for example. If you want to keep a relationship going well, you should try to do things that statistically make relationships go well. On the other hand, people are individuals, and if it's a good idea to modify yourself to be different from the statistical majority in some way, you can and should. Statistics are evidence, but not destiny.

• Curiosity.

Rationalists tend to have the attitude that the world is interesting. This means you will never be boring company. It also means you'll be willing to seek out new experiences with your partner.

• Not being a moron.

I never hear "judgment" among the top-ten qualities people desire in their partners, but I think it's more important than people realize. You really want to be with someone whose judgment you can trust and whose opinions you can respect. That doesn't mean "sober and boring," it means that you could trust your partner to be responsible for a choice that would affect your life profoundly (and that often happens in long-term relationships). Rationalists, if they're doing it right at all, have better judgment.

Short version:

• There are patterns in human sexual behavior and preferences that are perceivable anecdotally, or discoverable through research. These patterns can be used to make useful predictions.

• In order to create a certain outcome, it helps to fulfill the criteria necessary to produce that outcome. There is a strong incentive to self-modify towards traits that are attractive to the people you want to date, unless such self-modification is sufficiently costly in terms of time, money, ethics, and sense of self.

• Be as pragmatic as you can let yourself get away with, when needed. Don't be impragmatic unless you have a good reason!

• There is an incentive to self-modify one's sense of self in order to satisfy the requirements for the type of sexual or romantic outcomes that you desire, and in order to allow pragmatic self-modification in other areas.

• Learning how to date taught me more about my sense of self than my sense of self taught me about learning to date.

• Notice instances where an attempt at self-modification fails, or feels overly strained. If you can't figure out a way to make that form of self-modification work, stop it, and try something else.

• If you never strain your sense of self, you probably aren't being curious enough (or your current self is already sufficiently successful).

• Try to cultivate a self that will be successful for your goals (up to limits of time, energy, ethics, and empirically-discovered traits) without feeling that you are trying hard. Instead of constantly trying to micromanage your behaviors and traits, create yourself an identity that manifests those behaviors and traits for you. (e.g. if you want to date people who like athletic partners, then, within the limits mentioned in previous points, try to cultivate an identity and sense of self that makes you want to engage in exercise and feel that exercise is an authentic expression of your values.)

• The effectiveness of explicit verbal communication is limited, especially when not dating people who are nerdy with ridiculous IQ.

• Examine your view of ethics for false-negatives (i.e. things that you don't currently consider unethical, but should). A useful sort of question might be "if I was to try behavior X with 100 people, how many times would they have a negative response, and am I comfortable with that?"

• Examine your view of ethics for false-positives (i.e. things that you currently consider unethical, but shouldn't). A useful sort of question is "does this ethical principle literally ban a sexual or romantic behavior that the majority of the population currently engages in?" If you are holding yourself to a vastly more restrictive ethical standard than the vast majority of the population, then either everyone else are pigs, or you are being overly idealistic.

• Consider the outcome of other ethical theories than your current one, and the views of people whose ethics differ from yours. (Both for enabling or prohibiting behaviors.)

• The goal is not to maximize the average desire for you in the population, it's to exceed a threshold of people (with characteristics you want) who desire you strongly enough to actually date you.

• Self-modify to temporally disable analytical thinking (such as throughout this post) to enjoy being in the moment.

• Successful self-modification often involves forgetting what you were like before, and all these other bullet points.

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If someone wanted lifetime monogamy, and they got married at a somewhat young age to their first serious romantic partner, and they and their partner were very happy with the relationship for several years, up to and including the present day, what would you expect about this person regarding their relationship skills? Would you guess that they just lucked out, or that they are good at partner selection, or that they are good at relationship maintenance, or all/some/none of those?

If the person attributes their relationship success to very good partner selection skills, would you find that believable?

1. a. Communication is the key. Neither person, even if they are trying to be completely honest, is ever completely honest. Partially, this is because a person is not always honest with themselves. b. Sometimes being nice is worth a white lie. (Though I am still iffy about this one.)
   c. It's very important to analyze your own emotions. Why are you angry/happy/sad/apathetic?

2. a. Communication is the key, so "Don't propose solutions," but, rather, find all the variables first.
   b. It's important to understand what both people want from the relationship. Are those goals in alignment? If you have similar goals, then it's likely you can arrange your wants for maximum mutual benefit.

The major thing that improved my relationships was reading about feminism. In retrospect, this was a case where I had been generalizing from one example (my own experience), and ignoring the contrary data of others' verbal reports (confirmation bias; one argument against an army).