This question is asked of us again and again, as we get older, in various forms. At some point, "What do you want to be when you grow up" goes from a cute exercise, to the thing that keeps you up at night. Why? While this question inspires kids to dream about what they can be, it does not inspire them to dream about ALL that they could be.
Multipontentialite! Scanners! Renaissance Person! Polymath!
In a time when you may feel intense pressure to find your true purpose and calling...recognize that some are good at many things, and you may have an eclectic career path. Don't be afraid to try new skills & continue to learn about new ideas -- and think about the newness as tools in your toolbox.
It's rarely a waste of time to pursue something you're drawn to, even if you end up quitting. You might apply that knowledge in a different field entirely, in a way you couldn't have anticipated.
So, at any age, when thinking about what you want to be when you grow up, BE KIND TO YOURSELF and accept that there may not be a clear answer.