As I write this, I potentially have someone watching over my shoulder. My friend is sleeping on a couch behind me, he probably can't read my screen from that distance, and he's probably asleep, but there's always a chance that he can read this. Despite his quietude, he's present.
I have this image in my head of Radiohead's House of Cards music video where Thom Yorke's face is mapped by a 3D camera so that it looks like he's swimming in a sea of polygons.
It's like the frozen Han Solo's face extruding from the carbonite. What I see in these two images is how my awareness is drawn and teased away when others are in the room. I become partially less aware of myself and a little constantly aware of the other. Even if the other person is completely silent, sleeping in my room, extra resources are devoted to making sure I don't make any noises. Or let's say they're even sleeping in the next room, at any moment they could burst in, so I have to modify my behavior to prepare for that event. For example, I won't be doing naked yoga. That would make things awkward.
They also say that people who live alone, but have pets, lead healthier lives, both physically and psychically. One idea is that you develop more empathy. I read a study showing that children who grow up with pets develop more empathy. But perhaps, it has more to do with how pets impact your attention. You always, at minimum, have a background process running in your mind tracking their movements and needs. This creates enough of a distraction that you avoid over-thinking and over-introspection, two common causes of depression and dysphoria.