Day before my CPL/IR checkride I couldn't fly to save my life (literally - applying wrong way yaw on the simulated engine failure caused a swing the likes I've never seen before
). Couldn't fly approaches, couldn't hold a heading - the list is endless. I really doubted whether I should do the test the next day.
Needless to say the next day went without a hitch! We all have off days - the secret is not having them at the wrong time!