Because my high school Biology course (A Levels in the UK) was divided into modules assessed throughout two years I came to the last exam pretty sure that I didn't have to score many marks to get the grade I was aiming for.
I ended up in a weird situation where my instinct was to prepare really well but, in practice, I should skimp on revision for Biology and concentrate on subjects that weighted the end-of-year exams higher.
The strategy worked out - I hit what I was aiming for in Biology and in the other subjects. But that whole very tactical approach so went against my character that, to this day, anxiety dreams manifest about not having done the work for that specific exam. Often they're further exaggerated (e.g. I've simply forgotten to go to any lessons all year, etc) but it focuses around that event.
I find it weird that my subconscious prefers that over arguably even more stressful (and sometimes less successful!) exams at university. Maybe I was just more equipped to deal with it by then.