Odd thing used to happen to me when training.......
Before entering the helicopter, I knew all the theory and I was absolutely perfect in execution; probably up there with the very best pilots. When I got into the aircraft, my memory of theory somehow became corrupted, and to make matters worse I lost all the polish (and on occasions most of the wood) of my motor skills. I never could explain why....... odd magnetic effect emanating from the magnetos, perhaps?
Anyway, I can now confidently warn all of you that repeated exposure to the magnetic fields of the magnetos has now rendered my condition permanent. Untreatable. Although I have a license, I now am resigned to never again being in a position to confidently claim to know everything, and hope (one day) to raise my skills to "acceptable".
Something should be done about those darned magnetos...