I checked the John Gardner quotation in the NYT article, "The Problem with Meaning" by David Brooks. I also read the first several of the NYT picks of the comments. These add several important dimensions to the article. Your chosen quote, though, of the things you learn in maturity - is very well stated. I'm not sure if those things you learn in maturity are teachable. Another quote by David Brooks is in one of the comments: "Everyone is born with a mind...but it is only through introspection, observation, connecting the head and the heart, making meaning of experience and finding an organizing purpose that you build a unique individual self."
I speculate that introspection and observation might be teachable to a certain extent. Some people are very resistant to introspecting or have brains that are constructed so as to make it more difficult.