Now it becomes crystal clear to me: not saying aloud what I think and what I want is one of main reasons why other people keep on hurting me. It is actually quite obvious, but till now I only understood it intellectually. Recently I keep on realising: "hey, this person has >a< perspective, which is most likely >different< from mine, so why don't I tell them mine?". I think the core of the problem was that I was not recognizing that other people are separate from me and have different perspectives than I do. On some subconscious level I assumed they are part of me and know what I think, and if they did something against me I thought that was because they >want< to hurt me. That is a serious underdevelopment, something like before being 1 year old. Yes, I never got to the point when I understood the borders between me and the rest of the world.
And it feels so great to state what I think. It feels.. right. It feels like "finally, >someone< said the obvious aloud!", except it was obvious only to me :D Not saying what I think is the source of such an incredible amount of stress! And is crazy making. It's self-gaslighting actually.
So again, it was not occurring before to me that my perspective is different from the perspective of the other person, that is why I was not saying what I think. I thought it is obvious, and I didn't know why people keep on behaving inconsistently with it.
Something must have happened when I was very little that I got stuck there. My mum often points it out that I behaved as if I expected other people to know what I think. It's exactly this. She noticed it too. So there must have been something.