The teacher, not the lesson

There are two ways to build. You can niche down and become the person for one subject, or you can make yourself the throughline and let the subject change underneath you.

The difference is whether you zoom in on the lesson or the teacher. Bind your name to a single topic and you rise and fall with it. Bind it to the teacher instead, and you're free to teach different subjects across a whole life—the topic can move, and you survive the move. I'd rather be the teacher than the lesson.