I don't agree with Beagle on this one, learn from your mistakes. If the FI didn't make a big enough point of a mistake then maybe it wouldn't register as a mistake in the students head.
I know its a long way from flight training but I teach new employees to drive my road sweepers. Driving one of these things is like patting your head and rubbing your belly whilst driving. Everyone I teach can't believe how much concentration it takes at first and all agree it is like learning to drive all over again.
I let them make mistakes, then follow the hmmmm why did you get into this pickle route, then I show them what should have happened. I find this works far better than saying "don't do this and that cos its not right" it simply doesn't sink in as they are too busy concentrating on the new vehicle they are driving.
Maybe I shoudl adopt the "you have control" command as these machines have dual controls also.
Ben