It’s almost certain that you once had a test go badly. Whether that means you failed, or that you got a much lower score than you are used to depends on who you are and what your expectations are during a test. However, I would argue that the reason you had a bad test largely stems from the problem of not knowing where to start.
It’s interesting how I often hear other students say something along the lines of, “I can’t wait until we are done this course, because I can then forget about X.” I’ll also admit that I’ve been prone to saying these sorts of things as well. However, it’s interesting to me because it shows us how we place our knowledge into silos. It reminds me of something my mathematics professor said after one of our tests, “Yes, I put a physics question on the test. You’re all grown up now, so we don’t have to keep our meat and potatoes separate.”