The thing that is comforting to me is that for many classes the class average in terms of raw score is around 40-60%. Almost everyone misses issues or are not thorough enough in their analysis. I would go as far as to argue that for most classes everyone misses issues. The top students frequently only get 70-80% of the raw points available (or even less)
But yeah, I always find it annoying how 5-10 minutes of clear though after an exam has ended I become a sage who suddenly has the knowledge that if I had an hour beforehand would have gotten me an extra 10~ or so points.
As a 1L currently going through the exams myself, I left the first couple of exams convinced I was going to fall far short of where I wanted to be and was extremely mortified, stressed, and depressed about it.
At some point though I decided that assuming "I did very badly on that exam, my grade is going to be terrible" is less stressful than worrying "did I do badly on that exam or not?"
This might not be very helpful to you, but a little bit of pessimism has helped me with the uncertainty. I also salve over my wounds by reassuring myself that "even if I get a D here or there, it doesn't really matter in the grand scheme of things" (doesn't help all that much but helps interrupt the flow of rumination).
Edit: you might also want to consider searching a little bit about Cognitive-Behavioral Therapy and attention exercises (they help people distract themselves from intrusive thoughts, such as thinking about exams). I never had the patience to do the exercises for long enough, but they have proven to be effective.