It depends on how you define 'fail.' Here it is technically defined as an F or under 55%, however you can be dismissed for D's (56%-64%) or a semester average of C-(65%-67%). I have had several D's on exams, I have never had below a C- in any course.
My theory is that I start the semester doing as well as I can to build a buffer in for crazy classes. I map out all my exams ahead of time and try to be on the alert. During second year we had 2-4 exams or quizes every week except two. We also had professors that took random attendance and liked to call out and dress down students in the class. I always had a brief discussion with the professor to see if they had advice, talked to the top performers in that subject to see how they are studying, and did what I needed to get past it. Dwelling on it is damaging and unproductive.
I also learned to ask for what I needed. I did very badly on a practical in a microscope lab first year because I was blinded by the scope work and couldn't read the exam paper. It wasn't a problem in lab (lack of timed activity) but when I had 1 minute per question, I was blinded out. A filter helped immensely, and that professor smoothed the way for me over the next 2 years by explaining the issue to other professors, who didn't question his motivations (but may have questions mine.) I also attended a seminar on mnemonic learning for memorization and learned the peg number systems & some other methods that improved my retention of facts.