Other facts about how I experience this:
* It's often opposed to internal forces like "social pressure to believe the thing", or "bucket errors I don't feel ready to stop making yet"
* Noticing it doesn't usually result in immediate enlightenment / immediately knowing the answer, but it does result in some kind of mini-catharsis, which is great because it helps me actually want to notice it more.
* It's not always the case that an opposing loud voice was wrong, but I think it is always the case that the loud voice wasn't really justified in its loudness.
I've related a similar idea in the past to "Don't do something you know is going to fail". I'll do something like go to balance a knife in my mouth while I grab something and then say "What the hell? What if I fall? Why would I do this thing?". When I ask, I realize that there was a knowledge that I was making some tradeoff of noticeably higher danger-to-convenience than usual, and that I just barely noticed myself doing something that made no sense.
Over time I've learned to pay more attention to a sensation I think of as "Sneaking Suspicion."
Sneaking Suspicion is a "flavor" that some of my thoughts come with: it's a quiet little (metaphorical) voice that whispers "wait, but, are you sure?"
Lots of other voices in my head are much louder than Sneaking Suspicion. Sometimes I don't notice the whisper, even when in retrospect it had been whispering for years. But Sneaking Suspicion has a much, much better track record for honesty and correctness than most of those loud voices.
I notice that the people whose epistemics I trust the most appear to be extremely good at noticing their own analogues of Sneaking Suspicion. I think it's a skill similar to Noticing Confusion. But, at least for me, the term "confusion" doesn't really call to mind the right experience. It's not a "wha-- ???!" kind of feeling (Pikachu hurt itself in its confusion!). It's a lot more timid, and it has to be coaxed gently into speaking.