When my Physics course in (the german equivalent of) high school started, my teacher made us an offer: “For every single topic that we cover over the course of the next three years, you can hand me in a text covering what we learnt in your own words. I promise that I will meticulously proofread every text and give you feedback on how well you understand the material, how well it’s argued and how well it’s written.”
Three classmates took the offer, including me. Of those three, I was the only one to do this for every single topic. When I finished school, I had basically written a textbook on school physics, mercilessly edited by my teacher.
That practice has served me well ever since. I’m thankful for this opportunity and for the generosity that my teacher has shown.
I’m also baffled at how often people will just pass on opportunities to grow.