Start with lifestyle
Like most kids, I went through several different stages regarding what I wanted to become when I grew up. I remember wanting to be an astronaut and a pilot. I also bet I had a period when I wanted to become a cowboy - Lucky Luke was my hero. It didn't take too long for me to settle on wanting to become an engineer, which is what I eventually became.
That's great and definitely preferable to the lack of clarity that many of my peers went through. I had a passion for mechanical and electrical machines. Follow your passion, they said. So I did.
Well, it turns out career advice has evolved: instead of focusing on your passion, figure out what kind of life you want to have and find a "passion" that supports it. In the words of Cal Newport:
Fix the lifestyle you want. Then work backwards from there [...] What do I mean by lifestyle? Roughly speaking: a detailed feel for what your day to day existence would be like.
Steve Pavlina also recommends putting lifestyle first. He considers relationships and experiences the key parts of any good lifestyle design effort.
Figure out what kind of people you want to have in your life, figure out what you'd like to do and experience and come up with career options that would support those desires. Steve also rightly notes that the career you choose will also become a big part of your lifestyle, so take that into account.
The problem might come when you struggle to get clear on the details of the lifestyle you desire. For this, Steve also has a prescription: to gain clarity, explore.
Clarity through exploration
What's the best way to figure out if you like Thai cuisine? Reading and talking about it will only get you so far. You can take a guess, but if you really want to know, you need to try it.
That applies to everything. How do you know if you like sailing? How do you know if you know performing in front of an audience? How do you know if you like writing? How do you know if you like coding? How do you know if you like traveling?
You need to try it.
Of course, you don't have time to try everything. There's an opportunity cost to pay - whenever you spend time trying something, you're not trying something else.
You definitely need to start guessing and narrowing down the possible space of options, but at some point you also need to start exploring.
What would you like your life to be like? What could you start exploring today to confirm or discard your guesses?