I’m curious - has an authority figure telling you to abandon a project ever been for the best?
I just read a review and realized that yet again someone has written a well-received book on a subject a professor told me not to work on in grad school. This has happened three times so far.
“There’s not enough material on that for a seminar paper” —> Oxford UP book. “There’s too much material to make sense of, and it’s worthless anyway” —> a friend’s whole career. “I read your first chapters and you must change the topic of your dissertation” —> Cambridge UP book.
My fav: my theory in my entry for a prize for a paper on the history of science was judged so wrong that the prof decided to not award the prize that year. Now that theory is standard in that area of the history of science.
To the people DMing me to say they can’t publicly acknowledge their regret about abandoned projects because the authority figures who wrongly told them to do so might see - EXACTLY.
A friend just told me that in 1968, on the advice of her advisor, she turned down a Fulbright to study with Pierre Bourdieu. “The worse thing is that Bourdieu was so hot in 1968,” she said, and man oh man do I have to agree. 
Thank you everyone for the thoughtful replies and horrifying stories! I made a decision flow chart...
