There is still a notion that at the grand age of 20 or so, we should be able to pick a direction for our lives that will last until we retire. The Career. Woe to those who choose wrong!
Fortunately, that's hokum.
The glory of humans is that most of us possess more than one talent, more than one skill, more than one interest. That is why, of course, you hear that "but which one?" cry in the first place. The questioner is laboring under the assumption that s/he can only choose one and must live with it till death do them part.
A better approach, in my experience, is to choose something that you can live with for the next 5-10 years. Plan on changing careers. Hold that out as your reward, in fact, for making a choice out of all your choices.
I once heard a speaker at a professional conference explain that everyone should shake up their careers at about the 10-year mark. She wasn't saying you had to change careers every 10 years but that you should shake it up in some way after 10 years. If you don't? Burnout. We need change every now and then. It stimulates the neurons and keeps the blood flowing.
So, you're sure at 22 that you want to grab that MBA on your way to CEO-dom? Yes, you're just positive that you want to be a Captain (Captain? Heck! General!) of Industry. Well, go for it! But don't be dismayed when, in 10 years, you start to suspect that maybe now you'd rather be a veterinarian or a safari guide. It doesn't mean you made a mistake.
The mistake would be refusing to listen to your inner guidance and sticking with the "perfect" decision you made at 22. Or 32. Or 42.
I studied journalism in college, fired up to uncover corruption and fraud and be a beacon of freedom of speech. (OK, you gotta understand, it was the Nixon years.) Then I fell into the technical writing and have been happy here for almost 20 years. Now, though, I know that it's time to explore another side to my talents and in the next few years, I'll be moving into massage therapy. However, I know that I can't do that for 25 more years. I'm already contemplating, deep in the back of my mind, what I'll do after massage therapy.
Gotta keep those neurons jumping.