In SGTCIU, he really goes deep on the idea that pre-existing passion is unlikely to lead you to a happy career and presents an alternate, more-compelling framework for job satisfaction.
1. Acquire rare & valuable skills (career capital) 2. Use said career capital in exchange for job / life properties you care about (remote work, working less hours, working for 'better' companies, higher pay, more autonomy, managing more people, w/e those are for you).
There are happy & fulfilled people in every career and, of course, unhappy people in every career / walk of life. But pretty much everyone wants the same thing in their career: mission, autonomy, impact, and creativity.
These traits ^ are mostly independent of a specific job / field