It took me an embarrassingly long time to realize that (my 30's), and now I keep my conversations with my coworkers very utilitarian and divulge minimal information about myself. I try not to be a dick or anything, I'm polite enough, but pretty much everything I talk about is either directly relevant to work and/or so surface level as to border on "vapid".
ETA:
Just as an example, I used to have really bad sleep issues in my 20's that would make it so I wouldn't be able to get to sleep until around 4am, if at all. I made the mistake of bringing that up at work to my manager. Two weeks later I got a phone call at 3am because there was something he wanted to look at and "he knew I would be up". I was up, but I didn't really have much desire to get my laptop out and do work. I liked that job at the time and I liked my manager, so I did it anyway, and it wasn't until years later did I think about that incident and how utterly weird it was that I was sort of being punished for my insomnia.
My sleep issues have gotten a lot better now, so if someone calls me at 3am I probably won't hear it because I'll be asleep, but I remember that incident now and have it constantly spinning in my brain when I chat with coworkers.
* No
* Only if I get on-call pay
Still, I do think there's merit in keeping your personal life to yourself and not telling your coworkers more than they need to know. I'm not saying you should be stoic or a dick or anything; by all means engage in conversations and be nice. I'm just saying that it's important to have boundaries.
I tend to be someone who overshares a lot (hence my enormous word count on Hacker News), so I just try and keep this in mind.
Maybe I'm lucky. I've so far not had to endure a job for which I was underpaid and expected to meet and exceed every contractual obligation placed on me.
(otherwise where I work, I also avoid talking about politics for instance, but this is a different theme)
A) because picturing at my current work place everybody learning of all my opinions at once and the resulting drama
B) I am in progressive spaces quite often, but they are far from an echo chamber with everyone having the same opinions either ..
I received many strange requests like to come in Friday night while drinking at a concert and ransack the offices looking for a laptop or possible phone left behind that they suspected was triggering alerts by repeatedly trying to connect to a foreign server. "You want me to drunkenly rob the offices at night and walk out the lobby carrying a stack of laptops? Ok"