I don't feel that it always has to be an event. It can come from anywhere at anytime.
Often, it starts as simply a thought in one's head, that maybe they aren't this or that.
Mach, I had no idea it could work that way. I get that now...because of a thought or a comment...it's like I look for proof of why my thought is correct. And I'm feeding it.
I seriously thought I was crazy, or had some memory loss or must have blocked out some kind of trauma....because I had no "legitimate" reason to feel this way.