This happened in an examples class. The latecomers were drifting in so I started to hand out the examples sheets working from the front to the back of the class.

When I was done I turned around and already there was a student with his arm raised. Then another, then another. Pretty soon they'd all be signalling for help.

The guy who had his hand up first could only have glanced at the first question on the sheet for at most five seconds. That was enough time for him to decide that he couldn't solve it unaided, that looking at his lecture notes wouldn't help him, that thinking about it for another second was pointless. A few months ago this student was still at school, he had been good at this subject, engaged by it. Otherwise he wouldn't be here now studying it at university. Somehow in the intervening time, for whatever reason, that spark of interest, that ability, had been crushed.

Standing at the back of the class surveying this sorry scene was my most depressing moment in teaching. And then I had one of those rare cathartic moments. I felt a surge of adrenalin and I bounded to the front of the class. I was going to reawaken the joy these students once felt for a beautiful subject, reinstill their confidence, communicate the enthusiasm that I feel! This was my most inspiring moment in teaching. I hope I never lose that.