If you are asking the question "What do I want to do (or be) when I grow up?" here are are three other questions that might shed some light for you. If they don't give you definitive answers, they can at least get you started on the journey.
1) When you were a young child, what did you always think you would do? Those early years can tell us a lot about ourselves. They represent our character and personality before we were programmed by society and other life forces. Think about the things you absolutely loved doing then, too—and those you really didn't like.
2) What do you want to do when you retire? Is there some passion you're longing to express but always thought you needed to wait until retirement? Is there any reason you need to wait?
3) What do you want to do before you die? You may find clues to your yearnings and passions by exploring a bucket list or even a thimble list (the smaller things in life you want to do before it's too late).
Dreaming is good. So even if your responses don't seem practical, develop them and write them down. You can worry about practicality after you get several ideas on the table and once you create your action plan to get where you want to go.