When interacting with one person a disproportionate amount (such as a domestic partner), our mental models of other people tend to get filled with stuff derived from that experience. We think people will react the same, communicate the same, have the same base values. We have the same aversive or maladaptive reactions to situations that seem similar to ones that have gone poorly. We try the same tactics to defuse tense situations. And those other people? They’re probably doing the same thing with us, to some extent or another, depending on how aware they are of how their mental models work.
And we go and base parts of our mental model of ourselves on the feedback we got from our interactions with that partner. This leads to even more problems, because we think we’re good at [cooking / talking / sex], but we’re really not. Not in general, though we might be for one particular person, or really, just our mental model of that person, so hopefully at least that one model is fairly accurate.
These two things, when a long-term relationship ends, combine to leave many of us as a bag of screwy ideas of who we are and how to interact with other people. Codependency is a bitch. We’re not who we are; we’re who we shaped ourselves to be with that person. We don’t know how to interact with people; we know how to interact with that person. And we didn’t even realize how weird our reactions to certain situations were getting. Our friends tried to point some of it out, but we ignored them. Everybody’s different when they’re in a relationship, anyway, right?
And now we get to figure ourselves out again. If we’re lucky, we have a friend or two who have been around since before the relationship began and who are more centered than we are. If we’re really lucky, we remember who we were before. If we’re not lucky at all, we get to stumble around while we figure out what we really want, and not what “we” the couple wanted. And you wondered why nobody wants to date someone fresh out of a long-term relationship?
Now make that relationship toxic. Make the ex-partner abusive, manipulative, or controlling. Well, we’re in for a doozy of a time even figuring out what screwy shit we’ve internalized, much less undoing it. It’s therapy time.