Mentoring someone who is eager to grow.
When I was 15, I entered a high school physics egg-drop contest in which we were supposed to design the lightest container that would allow an egg to survive a drop from a water tower. I won, but was disappointed that the victory wasn't trumpeted in the next morning's school-wide announcements. That led me to introspect, and I found that (1) I was unconsciously seeking public accolades for my ingenuity; (2) I felt immature doing so; yet (3) I couldn't think myself out of the desire. I see that moment as the beginning of my conscious adulthood, as well as the defining crux of my life. It has been with me ever since, despite having tried a lot of things to grow beyond it. The only way to let it go, it seems to me now, is a single-minded pursuit of the aspiration until I'm exhausted of it.
In third grade, I returned to Japan after many years in America. My mother sat next to me for hours and forced me to read the text for an assigned reading over and over, so that I could read it fluently in class (something I would not otherwise have been able to do, given limited literacy in Japanese). Sure enough, the teacher called on me the next day, and I was able to read it straight through. That was, of course, just one incident. There is no single person who has done so much for me -- and so much of it well before I could appreciate it -- than my mother.
To be able to re-experience the world as a single whole, untainted by symbolic thinking.
There is no real progress without some change in people.