Problem is, one needs to be passionate about the right things from the very beginning -- and, paradoxically, the only way to decide objectively which things are worth being passionate about is to start off being dispassionate about them.
But you do not need to be passionate about the right things from the beginning. For one thing, it is possible to move into a field late in life and make enormous advances. Fermat provided a brilliant example of this.
Of course, you could say Fermat was an outlier, but I suspect that anyone who is truly, deeply passionate about something is an outlier already. Most people go through their lives with little passion at all.
I was passionate about zoology during some of the formative years of my life.
I realized later that unless I become the next Darwin, I will never be happy with my career choice because I will be doomed to working for a large part of my life for people less intelligent than myself and that I will not grow as a person because of that.
