This career counselor pretty much hits it on the head:
In part:
"I’ve come to the conclusion that we’ve been sold a bill of goods when we’re told to “Follow your passion, “ or “Do what you love and the money will follow.” Fact is, if you do what you love, you’ll probably starve.
Yes, some people do what they love and the money follows. But millions of people have followed their passion and still haven’t earned enough money to even pay back their student loans, let alone make even a bare middle-class living doing what they love."
Do What You Love -- And Starve?
But, I don't know how you'd actually induce a young person to internalize this information. Most are sure they'll be artists, actors, sports stars, or that they will stay kids forever.