Ugh, I had a mean jerk instructor. All she ever did was complain about everything I did wrong - it was like she couldn't just tell me what I did wrong without being mean about it. I never did anything right, based on her reactions.
Eventually she gave up on me (I'd like to think this was her failure and not mine) and I got an nicer instructor who actually made me feel like I could improve. I still had to drive with the mean jerk instructor the last time before my test, though, and I could tell she didn't think I would pass.
But I did, so she can go suck on a tailpipe as far as I'm concerned.