Mark Cuban wrote a great post in which he argues that time is your most valuable asset. How and where you choose to allocate your time is going to determine where your future takes you.
This reminded me of how colleges evaluate students. It’s easy to say that you’re passionate about something. But how much time have you actually spent pursuing this reported passion? For example, I’ve met a lot of students who want to apply to highly selective engineering programs because they are “very interested” in engineering. But saying you’re interested in something is a lot different than actually allocating your time to pursuing it. Have you taken any of MIT’s online courses that are open to the public? Have you read books about engineering marvels? Have you spent time restoring old cars, working in construction, or building your own computer? The time that you've spent actually learning about engineering is the best measure of your interest.
As you go through high school, think about how you’re spending your time. Allocate it carefully to things that interest you and that you enjoy. You don’t have to know what you want to do with your life or even what you want to study in college yet. But spending your time actually doing things will teach you a lot more than just talking about them will.