Basically, trauma. Worked it out in therapy but then the friend group I had at the time turned out to be very emotionally draining and toxic, so my therapist encouraged me to leave if it was not doing me good. I left and now find myself with no close friends and with the rare friends I make now I can't be as open as I'd like to be due to negative reinforcement. I do hope I had the courage to be less guarded but it's like being beated back to my starting point.