I’ll try to analyze what’s hiding behind this “passion” meme and, as a helpful exercise, rephrase the same message without using the word “passion” even once.
The key point is that academia is full of people who work very hard, and are very smart. If you want to be a successful researcher, you need to think how you could be competitive in such an environment. The possibilities for doing that are fairly limited. They are, roughly speaking:
You could be just as smart, and just as hardworking, as the typical researcher in your discipline.
You could be a bit less smart than the typical researcher in your discipline, but be more hardworking than the average.
You could be much smarter than the (typically already very smart) average worker in your discipline, which would allow you to work less hard than the norm in academia.
Individuals who can adopt strategy number 3 are very rare, so let’s assume that’s not a viable option. That leaves options 1 and 2, which means that, depending on how smart you are, to be successful you’ll either need to be very hardworking (the norm in academia) or very very hardworking — I’m talking about pretty extreme, workaholic levels of being hardworking here.
Now comes the part related to that word I said I wasn’t going to use. Ask yourself: how do all those hardworking people manage to be so hardworking consistently over many years? What’s their secret? And what is the chance that you can replicate such a performance?
The answer is simple. These people enjoy doing research. They enjoy it so much that it doesn’t feel like work. To them, going to the office or lab to work on research is as much fun as doing your favorite hobby. They don’t do it to get paid or in anticipation of the next promotion. They are a bit baffled whenever they hear someone talking of “work-life balance” (as if those two things are distinct and belong in separate compartments). Basically to such a person the whole concept of “work” and the connotations around it are quite different from what a lot of people (most people, I’m afraid) think of when they hear the word “work”.
So that’s all it is really. That word we were talking about is just a code name for enjoying something and wanting to do it out of intrinsic motivation and not because you are paid or out of a sense of duty. If you have it, it will not be a struggle to “work hard” because you wouldn’t be “working”, rather it will feel like you are playing a sort of fun game that you really enjoy.
And if you don’t have it... well, I’m not a psychologist but I think human nature being what it is, it will be an uphill struggle to maintain that level of hard work that others find effortless over more than a few years. At the very least, you’ll be at a serious competitive disadvantage, so you need to think what advantages you do have (being unusually smart, unusually creative, unusually good at collaborations etc) that could offset that disadvantage and allow you to still be successful.