My friend and I were discussing a shared acquaintance, who found himself suddenly single while his girlfriend was out of town. I bet the house is a mess right now, I said. Oh no, my friend countered, in fact, it's the opposite. He's pretty much organizing the spices and learning calligraphy to hand letter new labels for them. I'm guilty of sleeping with the light on and everything — books, computer, iPhone, camera — piled on the bed around me. Another friend leaves towels and clothes where she drops them and only picks them up when she knows her husband is on his way home. A third friend sheds his clothes the minute he walks in the house, something he doesn't do (well, not that often at any rate) when his (non-romantic) roommate is around.
For the sake of harmony, most of us try to keep our more slovenly or weird habits to a minimum when there's another person around, no matter how intimate with them we are. It's only when we're living alone, even temporarily, that we figuratively spread out and get comfortable in a way that we won't when we're sharing a space. Of course, not all habits, quirks and ticks are unattractive ones. The friend we were discussing, as a matter of fact, usually uses his time in solitary creatively, with movie and friend marathons and, often, an intensive and obsessive home project with which he surprises his girlfriend when she comes home.