I lived alone for a very long time after roommates became too much of a stressor...

I lived alone for a very long time after roommates became too much of a stressor, and it was pretty cool. Nowadays I live with my girlfriend, and it's quite similar to how you describe it. We end up developing shared quirks or quirky ways of communicating.

Living with someone has weird effects though. I've forgotten how to get or prepare only enough food for one person at a time.