So the adult says that it’s hard to make a living in the performing arts, which is true; and the Young Person Dreaming of a career says the adult doesn’t understand, which may or may not be true. But even if the adult was once a y.p.d. herself—even if she’s now a successful performer—the advice is unlikely to have any influence, because the y.p.d. sees it not as a statement of fact but a test of his commitment.
The adult plays into this by saying, “If you can be discouraged from a career, you shouldn’t try for a career.”
Bad move! The y.p.d. responds, “Excelsior! I cannot be discouraged!” And closes his mind to the very real doubts that have been plaguing him.
The conversation that might be useful to the y.p.d. and interesting to the adult is thus short-circuited.