This reminds me of when we were doing our circuits on the A330. I was sat in the jumpseat, and one of my colleagues was sat in the right hand seat doing his training. It was his first ever time at the controls of a heavy aircraft. Part way downwind I saw the captain looking across at him with a concerned expression. I leant across to look at the FO, who had literally gone completely white. He looked like Casper the Friendly Ghost. There were beads of sweat on his forehead and he had completely frozen at the controls. The captain asked him if he was OK, and the FO stayed completely silent, staring forward with eyes as wide as saucers. He couldn't even speak.

Up until that point he had been so confident in the sim, and had great theoretical knowledge, but once at the controls he fell to pieces.

I wonder how often instructors see this type of thing?