Teaching matters. And it's hard. Anyone who tells you otherwise (on either score) isn't trying hard enough.
My goal in teaching students in the earth sciences is for them to more fully understand and appreciate the world around them. To achieve this, I teach with a focus on process, take student learning into the field, encourage student-driven exploration, and make research and teaching seamless.
Figuring out how to create intellectual space in which students can discover the concepts at hand, and then executing that plan, is enormously rewarding. Those are the moments when you are reminded that all the work has been worthwhile.