It's good to know what you don't like
This particular young relative had wanted to be a fire fighter for a very long time, at least in "young people's time." (A year for me is like almost nothing now, it's scary. When I was little, an hour seemed like f o r e v e r...) She recently told her mother that she had decided that she didn't want to be a fire fighter. Her mother asked her why and she said, "Because I don't like smoke."
It's good to know what you don't like. In college one semester I found the several-hundred-page course guide so overwhelming that I cut out all the pages from the departments that I knew I wasn't interested in (Physics, Earth and Planetary Sciences, East Asian Studies), so it wouldn't be so hard to choose from what was left.
I also went to a career fair there once and discovered a plethora of careers that I was emphatically not interested in. That was something of a relief--no need to go through the recruiting wringer, etc.