Working in a different room (NOT your bedroom) is critically important to me. Sometimes it's fun to kick back and code, but the separate space that is yours, optimized for work, and assigned mentally to work is useful in that you can walk away from it and also leave your work behind. Going to bed at night with your laptop stashed close by does not inspire relaxation / restfulness.
Last year we moved out of our old (large) home in Philadelphia, where I had stolen the back 1/3 of the separate garage to be my office. My commute was about 50 feet, but it was to a separate (physically, acoustically, psychically) building.
Now we live in a lovely but much smaller house where I still have an office, but it is inside the house. We've been here for 9 months so far, and we have still not really figured out the details of how I can still "go to work" the way I used back in Philadelphia. My wife only has to speak here, somewhere in the house, and I can hear her.
This may improve when some specific physical details are addressed, but I think they won't solve the whole problem, which is a psychological/emotional/relationship one: how to be in the same "space" as someone else but also make it clear that you're not available.
Totally. This took us months to figure out, even after a lot of "hey this is gonna be hard" pre-planning. I started by sharing Rands' "Nerd in a cave" post among others talking about interruptions and remote work (https://randsinrepose.com/archives/a-nerd-in-a-cave/) - my reactions were... uh... not the most civil initially haha - but then mostly tried a number of things until we got to "as much as possible, please try to contact each other like we're in an office" which is a good convention.
We figure out the schedule of the day before I head "in", we communicate via text, and if that fails typically it's a knock at the door just like in an office. I also mention when I have big meetings or other face-time meetings so there's awareness.
That said, after all of that it was really the threshold for things that caused interruptions was what took the most adjusting.
Most of the day I wear headphones and listen to music, which is helpful - you don't feel compelled to shout answers or run down and help unless the person asks. Eventually though we found our rhythm, and it works well. And we both appreciate that when we need each other, we're right there, and that's great.
Through the joys of expensive real estate I don't have the luxury of separate rooms but personally I've never found it that important. I have a desk that is almost exclusively used for work that seems to fill the role, but even that is more for ergonomic reasons than anything. I feel the social isolation others mention, but that's solved with more regular nightly visits to the pub.
The big thing I need to improve on is simply getting outside more and going for walks during the day. A significant part of my commute was walking and now that's gone.
I recently started working from home, which coincided with a move. This is the specific reason I insisted on a two-bedroom apartment. I think it's made a big difference. I was remote before this, but had a private office in a WeWork, which I went to everyday, even though it wasn't required. This kind of separation is crucial.