It is easiest to change someone's behavior through appeal to emotion. Like a sledgehammer, emotion is a blunt force on the psyche. But if you want to give a child a tool to shape themselves autonomously, it is much better to teach them to think with concepts. Concepts are like scalpels, capable of precise cutting -- and they work through a more delicate psychology of feeling.
The best teachers use emotion to hold at bay the forces that threaten the preconditions of education. Love and care are essential tools in this respect -- and sometimes even anger. But once the space of education has been constructed, it's best to minimize emotion in teaching. Play is the avenue to a nuanced psychology, capable of wielding the more precise tools of the intellect.