That message is such BULLSCHIT! Don't believe it.
The example he gave of him following his grandfather's passion does not make this true.
Perhaps most people do not follow their passion. Instead they accept someone else's beliefs, before they have had a chance to develop and trust their own. Or they believe someone's advice "Get into plastics!" and are possibly miserable their whole life, even though they might make a great living.
Bull!
Spend your time doing what you love to do.
Too many years of fiberglass and epoxy getting under your skin?
You are correct though, one has to define what they're idea of success is and go for it, screw everyone else. If it doesn't work, chock it up to life experience, reassess and move forward. Too many ways to make a living doing what some else defines for you.
