I can pick up a sense about someone, by the way they act or what they say (or don't say), but I'm not a mind-reader and don't know what they're feeling unless they tell me.
Growing up it was almost expected that I was supposed to "know," so I was always guessing and living in anticipation of everything, and of course if I read someone incorrectly it was my fault. And it kind of screwed with my head because I thought that's what people did, so I learned not to say anything, but then I would also be disappointed when people weren't "reading" me and didn't act the way I liked. And if they were direct with me, it would freak me out because I wasn't used to that, either.
Never really learned to say what I felt - or even that I had a right to say it - until I was an adult, and even then it was a learning curve. I've even been called on it a few times by trusted friends, who make me feel safe enough about it to acknowledge, "oh yeah, you're right." As I've gotten older I think I've gotten much more bold in my directness, and in doing so I'm also noticing 1) I'm more and more comfortable with other people who are direct, 2) more aware of how much people aren't that way, and 3) more aware how some are taken aback by what I say. And I'm not even saying anything unkind, just speaking straight.
Makes it so much easier though than to try and "read" each other.
Body language is something we should all attention to, because quite often people say things when questioned that are not true, but their body language gives them away. In general terms in relationships it would be a lot better if people made clear what was on their minds instead of expecting others to read their minds. In my experience this problem is common with married couples!
Yeah. We rely on reading people and hide behind polite-ese far too much IMO. Open communication is a skill that has to be learned and it can be scary to lay out who you are warts and all. I think it makes for much better relationships and mental health.