Marital bliss (or whatever the equivalent to shacking up would be) surely depends on two things. A house with more than one floor (even a basement will do) and separate clothing closets. Skip either at your peril.

One's signficant other might not grasp your desire to be (or not be) fanatically organized. Do not make your daily ritual of getting dressed depend on confronting this harsh reality over and over again. Get your stuff into another closet and never look in theirs again.

As for floors, nothing helps soothe tensions like having to expend the effort to mount the stairs. Better to have a floor between you if/when something too trivial to bother with comes to mind. It's amazing what sorts of trivial crap can be ignored because it would involve walking all the way up/down a flight of stairs. That and spousal selective-deafness always comes into play when the other tries being lazy and shouting it from another floor.

Trust me, 2 closets and 2 floors. I'm sure there's other tips but these have worked time and again.