A dangerous thought
There are some thoughts you remember explicitly because you try to forget them. This thought I tried to push down because I was so tired when I had it I knew I would misinterpret it and end up irrevocably changed, like a driver who knows he's going to crash if he doesn't stop to rest.
I was socially anxious as a kid, mostly because I was shy and bookish. I was very afraid of talking to other people, especially in large crowds. At some point during puberty I got rid of this fear mainly because I realized I didn't care about the opinions of the average person in a large crowd after reading many terrible opinions online. This allowed me to suddenly become much more extroverted and socially courageous, because I would truly believe that nobody would remember or care what I had done. This made me a better public speaker and better socialized, because I would seek out opportunities I didn't seek out before and I was less nervous, which always helps with talking to other people.
I was thinking about recent times I had felt true fear, and the terrible thought was this: the arguments above could also apply to exams. Exams are not the only way to conceptualize topics, and are often shaped by the biases -- terrible opinions -- of other people. My fear of test results is also irrational, and probably leads to worse performance on those tests than if I had not been so scared.
In retrospect, it was weird that I didn't realize this earlier, mostly because of my history in Science Olympiad. Those tests were truly terrible, but I was dumb enough that I didn't really realize (other than pointing out obvious errors that still could have been made by a smart but tired person).
Maybe the terrible thought is actually this: that by that logic, I should just not care about exams. They are poorly-designed obstacle courses where the obstacles don't represent the tested concepts and the actions you do don't represent real application.
But I believe that all beliefs should serve a purpose. One purpose is putting desired events into motion. Some beliefs are better at generating that outcome than others. It's like having correct mental models in sports. They aren't designed to represent reality, they just provide you with a mindset that can get you the results you want.
If believing other people don't care about what I'm thinking leads to that outcome, then I should believe that. I think the main difference between socialization and exams is that this mental model is only helpful for the former, if your goal is to get good grades on exams. You can't fully engage in a system you don't believe in.
So I guess the true dangerous thought was that I can confuse beliefs I have for their outcomes, and beliefs I have because I truly believe them. The exam thing is true, but not useful for achieving the goals I want.