On the contrary, I'm usually optimistic.
You've never been in a situation like I have been before, then. I've never failed a test, but there have been times I thought I would.
This aside, I asked if you've ever been pessimistic about a test. Not how you usually feel.
I have failed a small number of tests in my day (none in highschool, mark you). But I'm always optimistic, regardless of how easy or hard it is. It sometimes takes weeks to get tests back, and the last thing I want is to be worried for all that time. Plus, I have reasonable confidence in myself that, even if I knew shit about the subject matter, I can still BS my way through at least half of it. And normally, that's true.