It all sounds pretty similar to my experience. Living with my family (parents, siblings, cousins) has grown increasingly stressful over the past decade or so, though, so I find that things are usually (not always; sometimes we get along just fine and it's fun times) worse when I'm there.
I recently did a quick-and-dirty quantifying of different aspects of my life during different time periods, and found exactly what you said about "given" social interaction to be true. My first two years of college were horribly unpleasant and unproductive, and were also the two years that I was most alone (I didn't recognize this and was stubbornly clinging to individualism at the time); the same is true of the two years I spent at home after college (except by then I'd realized my folly; it was just absurdly difficult to do anything about it by then).
I also find myself with an irrationally negative emotional reaction whenever I so much as think the word "lonely". "Lonesome" is slightly better, and "alone" is significantly better, but I still feel strong resistance to breaking the taboo on talking about it. (I was actually considering posting to see if there was any interest in an LW meetup anywhere I can reach. I'll probably just wind up trying to make the St Louis meetups if I can level up my ability to travel independently.)
What I want to get people to discuss here is obvious given the title. What has been their experience regarding who and specially how many people they live with, and how that impacted their motivation and happiness.
I don't want to peruse papers on happiness and productivity, because I'm particularly interested in anecdotal tales coming from a Lesswrong sample.
Three pieces of information seem relevant, so if that is okay with whoever comments, I'd ask people to tell us if they consider themselves introverts (recharge batteries by being alone) extroverts, or both. As well as their age and hometown.
The reason I want to have a fuller understanding of this is that I've slowly come to have a strong belief that the main problem with people I know who are suffering, or failing to achieve their goals, is living with fewer tribal affiliates than they "need". And that belief could very well be false or biased.
I'm equally interested in what people think in general about their friends' living situation: "Most of my friends who live with friends experience such and such emotion, but the ones who live with family experience such and such problems with motivation"
as I am in personal experiences.
Following a suggestion about creating topics like this before, I'll put my own case in the comments.