Well, if that nightmare scenario came true, I’d tell him or her to realize that nothing in life has any real objective meaning
Arguable.
and no one really has your best interests at heart
Untrue.
and that you should pursue only what you find interesting or exciting and not waste a second of your life doing what society claims is good for you or attempting to live based on what other people want or think.
Possibly true, but you have to be prepared to accept the consequences of doing so.