I play keyboards, write songs and produce music either for my own groups or other artists.
Well, every day is different. If I have a gig in town, I may leave early in the afternoon to set up and soundcheck. Then go get something to eat and then play the gig (usually later in the evening) and get home late. If I have a gig out of town, I would usually fly out the day before, fly home the day after. If I'm producing an artist I'm working either in my home studio or at another studio elsewhere. If I'm doing none of these things then I'm writing and recording at home.
Playing with all kinds of musicians in all kinds of styles. For musicians starting out, the best thing is to find other people to play/record with. Record using Garageband or whatever you have, just to get experience. But the absolute most important thing in my opinion is having a "sense" for what the music needs. There is no one way to get there. A few people have this naturally, others have to develop it. Listen to a lot of music, play a lot of music. Study it, dig deep.
Here's the first step for high school students
Pay attention to English classes (especially poetry and creative writing). You'll also need to be good with computers and know your math. Really all of your education will be helpful. Also, get involved in high school music programs. And find other high school musicians to jam with and start honing your chops.
"You don't have it, you don't have a good voice, etc."