I got in the habit of leaving the door open when I lived with my mom and our dog Hiebert, because he liked to come in the bathroom with me, and my mom and I never really established any proper boundaries.
My husband likes for bodily functions to be private, for both of us, to keep the sexy in our relationship. Even when he's not home, I keep the door closed, just so I stay in practice and don't forget when he is home.
While he was away for a few months, I did start leaving the door open. It's quite liberating.