Many moons ago I was teaching a rather serious Gaswegian on his own Terrier. A solo flight was taking a long time to come, and he was getting totally depressed. I then made him fly a cct in a club 150, which went off without a hitch, including the landing. I pointed out that he could fly, just chose a difficult aircraft to learn in. Back in the Terrifier a solo came quickly, with me standing by the runway. A smooth landing ensued, and as he slowed to 3 or 4 mph a little smile (the first ever!) broke out on his face. At that moment the a/c did a slow and gentle ground loop to the right, I never saw that smile again!