It started well before, definitely in undergrad but possibly even before that (perhaps in a different form). It stems from another more general fear, of not doing things I'm supposed to be doing without realizing it (classic academia fears - like the common exam week dream where you realize you are registered in a class but forgot about it and never went, which extends into waking life and you get this nagging fear that you actually forgot about a class). I have also just always been awkward interacting with people, so it was a deadly combination.
Then in grad school, I ended up with a terrible adviser who never offered any help or support or even general guidance as to what I should have been doing, and who would then berate or criticize me for not doing things right. He blamed me, and refused to write letters of recommendation when I tried applying to other programs, scuttling my academic career.
I learned a couple years later that in ~25 years as a professor at that school, he's never had a grad student who actually graduated.
(the real lesson is not to not go to grad school, but to do your research before you do)