The best teachers I know are also the best learners–they are constantly learning about not only their subject area, but teaching methods, educational theory, and things that are of personal interest. They model (often without even thinking about it) what it means to be a lifelong learner. Maintaining the mindset of a learner makes them good teachers.
The line “Above all, it’s the emotions elicited by teaching that make it such a powerful vehicle for learning” really jumped out at me as well. I’ve been doing a lot of thinking and reading about motivation and resiliency this summer; I wonder if students who struggle with being invested in their own learning (for whatever reason) might find motivation in helping someone else with their learning. It’s an interesting combination of intrinsic and extrinsic motivation.