Jacob Falkovich says that single people often seek out similarity when complementarity is what makes relationships cohere long-term. It’s a great observation. But how to operationalize it? Maybe: look for someone you can’t initially understand, but also don’t feel like walking away from.

Of course, we rarely approach relationships with such wisdom. Instead, we spend years failing to fully commit to any one relationship—either by finding a reason to call things off as soon as a serious liaison starts to look likely or by only halfheartedly showing up for whatever relationship we’re in. Or, alternatively, in a pattern that every expe... See more