You have time. In fact, you have all of eternity, but the chance to decide, and to influence, what happens on this far-flung steppe of Time will last but an instant.
What is important for you to know is that you do get decide.
Mainly you get to decide what matters to you. If life is about anything, it's about the ability to make that decision. But I know that's hard for you to figure out right now, so I'm going to spell it out for you.
Is it music? You're only 16. If you dedicate yourself entirely for the next ten years, you will have a musical career by the time you're 26. This is young, by the way.
Is it writing? You will have a best-selling novel by the time you're 30. But you have to be disciplined about reading and about writing. 30 is still young, though.
Do you want to be wealthy? Go to business school. Study your ass off. Wear suits. Get hired at a consultancy. You'll be a millionaire by 35. Yeah, that's young, too.
You want to keep running? Hit the gym hard. Eat right. Aim for a track scholarship. Maybe you won't make it to the Olympics, but you'll be fit and you'll have made a habit out of the healthiest of lifestyles. Might as well start now, because it gets harder every year.
Want power? Join a political party, take a public speaking course (take one anyway), go to law school. Study hard. Put in the time and effort, and, by the time you're 50 you could be its leader. That's young in politics.
I think you get the point. The specifics are not important. What is important are dedication and discipline. And that these surpass any interest in the things that don't matter.