It's almost a foregone conclusion that you should "follow your passion" in your work life. You'll find yourself much more engaged in your work, people say, you'll enjoy your work more, and be all-around more happy about your work situation. All that makes sense, of course.
While passion is great, I'd disagree that it is the key to a successful career. Passion can help. But it can't beat endurance over the long haul.
Passion is an intense emotion, allowing for great focus. But it takes a great deal of energy to maintain that level of emotion. At some point, perhaps even less than a year, the passion wanes. You look up and see that all of what lies ahead of you no longer has the meaning it once did.
You burn out.
I am a non-practicing ham radio operator. It was a most interesting hobby for me for about 15-years. The reason I liked the hobby so much was that there was a variety of pursuits you could take within the hobby. Tired of this aspect (trying to contact as many foreign countries as possible, for example)? Change and pursue bouncing signals off of the moon. Tired of that? Go build stuff.
It was all related to the hobby of ham radio -- but none of the pursuits lasted more than 3-4 years. And even with all of the different aspects of the hobby to work with, all of it didn't last for 15-years.
And this was for a hobby. I did that for fun. Not work.
So our passions change -- it's not so easy to casually throw off one career for another just to follow our passions.
Look, your work isn't just about your work. It's not just about the mad scientist running tests, the project manager managing projects, the doctor practicing medicine. It's about finding meaningful work.
Your career is also about companies that grow, change, get bought out, or die. It's about the great manager that gets swapped out with the lousy manager as part of a reorganization.
It's about the cost cutting, site closings, mergers, acquisitions, stock prices, relatives in a family firm, and dozens of other things that you need to deal with in order to stay and do your work.
Your passion gets beaten down. All. The. Time. Working for a company means dealing with all of that stuff -- good, bad, and indifferent. Sure, you might get by without that other stuff if you ran your own company, but the reason I focus on people who work in cubicles is because most people don't run their own company. Nor do they want to run their own company.
Which means you need to endure. Endure the work, the changes in the company, the changes in management, and the changes in yourself as you learn and grow. You need to pick a career where you think you can endure.
Over the long haul, endurance trumps passion.