I know at my very worst my ability to judge my own mental state is the very first thing that flies out the window.
Physical damage or impairment, I don't know. Could be I simply walked down the wrong path at some important stage of my mental development. I've had doctors and therapists suggesting it's some kind of PTSD stuff, but I don't think so. All I can say for certain is that things got strange in my later adolescence. When I was twelve years old I knew everything, I was certain I understood the world. At nineteen I was a hot mess hurting everyone who cared for me.
My current meds seem to be working, but I don't like them. All I really know is that I end up in the hospital if I quit taking them, or their effectiveness fades. I landed in a locked psych ward just last year, danger to self, thankfully not to others... physically at least. I can say things that are incredibly hurtful to those who care about me, and in times of despair I wonder how I'm worthy of any sort of human relationship. (My crazy grandma had a similar capacity for saying mean hurtful things, but she could also be a danger to others, which is why she had to be removed from the home she owned, not because she was a danger to herself, nobody cared at that point because she'd burnt all her bridges, but because she was a physical danger to others. She was cussing up a storm and trying to bite the paramedics after they'd strapped her to the gurney.)
I've got more than forty years experience striving for some no-meds nirvana of "normal" people, but so far, no success.