How much people can learn at any moment depends on how they feel at that moment about the task and their ability to do the task. When we feel powerful and competent, we learn at difficult tasks. the difficulty does not discourage us, we think, 'sooner or later, I'm going to get this.' At other times, we can only think, 'i'll never get this, it's too hard for me. I never was any good at this kind of thing, why do I have to do it"
Part of the art of teaching is being able to sense which of these mood learners are in. People can go from one mood to the other very quickly.
The real point of the story is that the best game with little children flows easily and naturally from the situation of the moment.