Why don't you have to take into account the prior probability of the large mistake that occurred? Of course, you might be biased and believe it to be smaller than it truly is, in which case there should be a whoops moment (your mistake was overconfidence), but clearly there must also be cases in which there was a small prior probability of a big mistake. Shouldn't we not judge these cases by only examining the outcome?
Can you imagine the reductions in the number of students able to handle coursework if professors actually made their students think rather than memorize.
Unfortunately, it seems that most universities are obsessed with making money and thus need to address the abilities and intellect of a wider audience... not everyone is capable of the upper level critical thinking suggested here.
It's strange that it sounds like a rationalist is saying that he should have listened to his instincts. A true rationalist should be able to examine all the evidence without having to rely on feelings to make a judgment, or would be able to truly understand the source of his feelings, in which case it's more than just a feeling. The unfortunate thing is that people are more likely to remember the cases when they didn't listen to their feelings which ended up being correct in the end, than all the times when they were wrong.
The "quiet strain in the back of your mind" is what drives some people to always expect the worst to happen, and every so often they are right which reinforces their confidence in their intuitions more than their confidence diminishes each time they are wrong.
In some cases, it might be possible for someone to have a rational response to a stimulus only to think that it is intuition because they don't quite understand or aren't able to fully rationalize the source of the feeling. From my own experiences, it seems that some people don't make a hard enough effort to search for the source... they either don't seem to think that there is a rational source, or don't care to take the effort.... as long as they are able to ascertain what their feelings suggest they do, they really don't seem to care whether or not the source is rational or irrational.
A true rationalist would be able to determine the source and rationality of the feeling. The interesting question is if he fails to rationally explain the feeling, should he ignore the feeling, chalking it up to his weakness as a perfect rationalist.
Since we are all human and cannot be perfectly rational, shouldn't a rationalist decide that a seemingly irrational feeling is just that, irrational. Is it not more rational to believe that a seemingly irrational feeling is the result of our own imperfection as a human?