The Week recently posted an article by Eric Barker, the well-known blogger ("Barking Up The Wrong Tree").  The title: Seven ways to be the most interesting person in the room. Now, "interesting" need not imply narcissism or snobbery. It simply helps people avoid being a bore, which apart from anything else is an essential ingredient in the stew we call good manners. And, of course, it includes the imperative to be interested in others, as well. Eric concludes his piece:

And most importantly: Live an interesting life.
Remember the theme of Don Quixote: If you want to be a knight, act like a knight. If you don't read, watch, and think about generic things, generic things are less likely to come out of your mouth. This doesn't need to be expensive or difficult. Hang out more often with the most interesting people you know. The friends you spend time with dramatically affect your behavior — whether you like it or not. The Longevity Project, which studied over 1000 people from youth to death had this to say: The groups you associate with often determine the type of person you become. In The Start-up of You, Reid Hoffman and Ben Casnocha talk about how the best way to improve particular qualities in yourself is to spend time with people who are already like that. The best and most reliable way to appear interesting is to live an interesting life. [Emphasis ours] And to pursue that ends up being far more rewarding than merely making a good impression on others. [Though being somewhat impressive can give a major boost to your self-image and confidence.]

Hmmm. Sometime in your late teens sounds like a good time to start embarking on great adventures in interesting places with interesting people—adventures that will shape your character for the rest of your life.