My psychiatrist laughed at me when i said i was "smalling" my life, but that is what finally calmed me down and stopped triggering my too-muchness, as you describe.

Is it nature or nurture? Idk. Did anybody ever STOP pavlov's dog from salivating at a bell?

Looking at it another way, true self and false self - the hyper overresponsive me is definitely my false self, goaded on and teased by others all my life. So when the teasing stops, and the overreactions stop, im left with a rather empty true self.