Career paths??? When & What

Hello! When school starts this year, I’ll be a junior, but I was wondering: when do people start thinking about career paths?
In my country, all high schoolers must decide whether to go into the sciences or the humanities in their junior year. Luckily,
it seems you can easily change around what you want to major in for college in the U.S., but still…
I used to be very interested in science when I was younger, but recently it just doesn’t seem to click with me anymore and I’ve found a new interest in writing stories. However, a career in science would lead to a more stable future…? Is there some way people decide on where they’re going to go in life???