I shop for myself. I don't have to worry about budgeting for things that other people eat that I don't eat. I don't have to worry about taking other appetites into account when getting perishable treats such as the container of strawberries that I haven't entirely devoured yet. (Erk, since they're slightly frozen, I think I have the refrigerator temperature a touch low.)
I am the only person using certain items such as the laundry quarters, the laundry soap, the toilet paper, paper towels, shampoo, soap, garbage bags, the long distance on the telephone, the electricity ... if it has to be refilled, I will be the one doing the refilling, and I will be the one who does not suddenly realize that someone who does not have the responsibility for it has been using it so that when I need to use it, it isn't there -- and this is good. I have both control and responsibility.
No one else is messing up my kitchen. No one else is leaving the seat in unusual positions in my bathroom. (I did not previously share a bathroom -- the bathroom was my domain. When a bathroom is not equally shared between persons of differing bathroom habits, it is meet to put the items back as previously set.) No cats are rampaging through my laundry, laundry that often is carefully stored on the floor.
No one else stacks dishes in the sink. No one else touches the sink, for that matter.
The apartment's smaller, of course, but I have more space that's unquestionably my space. I don't have to worry about coming in late and waking people up. I have friends from work who drop by, and I socialize with my writing group.
One of these days, I'll come to terms with the idea that yes, I'm a grown-up.