Do your best in school and what you like, and consider things you want to experience after school, like traveling or college. Now is a good time to think about this sort of stuff while you have the opportunity to do so; life at this age is an open book, you can do pretty much anything. I feel like I've wasted a good chunk of my life on being depressed at that age, so I encourage you to grasp and enjoy it. You could try new things, such as a sport or club, or even volunteer work. Try not to chase inspiration, because it likes to breeze in at the most unexpected time.
In a way, I know exactly what you mean: I also felt like this. Actually I felt like this until I was 19: Life was meaningless, having no purpose. I mean, you get born, you grow up, you finish school, you work, you get married, you have babies, you die. I don't know about you, but knowing that life was nothing more than this kinda made me feel that it wasn't even worth living it. Now, don't get me wrong, I wasn't depressed or suicidal - I was just very unimpressed. Life didn't have much to offer.
Right now, I don't feel like this anymore: When I was 19 my mom decided to start dragging the entire house-hold to church. I decided to give this "God-thing" a chance, and realized that God was real after all. And to make things even better - He has a purpose for every single one of us - He made you, and He had a specific idea in His mind when He made you - You see, He has plans for you "For I know the plans I have for you," declares the LORD, "plans to prosper you and not to harm you, plans to give you hope and a future." Jeremiah 29:11
You might discard this as nonsense, but I was a border-line atheist and God proved Himself to me. Please read my testimony here [link] You are more important than you might think - and you might have a purpose beyond anything you have yet thought about.
Thing is, soon you will be an adult and it's normal that you make these thoughts, you will probably go to college and you wonder what you will become, what you want, which road is the right one for you etc. These questions are hard for anyone else than yourself to answer, but there is no need to panic, you still have time, people are in their 30s and yet don't know what to do with their lives. It's also normal to be introverted, you know how much introverted I was? I had someone who ALWAYS hit me exactly those words on my head, and said that it would change with time, and it did. I feel totally different than before, and it feels great. I also didn't know what to do with myself, which road to follow, but guess what, everything turned out well today everything has to be fast and I'm sure you have friends that know their road etc, but it's not necessary that everybody knows their way, not in the same steps and pace, you are unique and you will find your way when the time comes
just pick one small goal at a time, and put your focus on it. As time moves on, your understanding of how to direct your values to goals will grow. That's how purpose is established - it's not always one big move. Learning and dialing in your perspective is no small task - making things real takes practice and many tries.
Pursue whatever you want. Enjoy what you have now. If you're too busy focusing on the big things, you neglect the small things. And you won't know the impact that those small things have on you until they're gone.
Thinking too much can be bad for you. I used to do that, but then I realized that there's not really much I can do to change them so I suck it up and keep going. I teach myself better discipline and patience because I've come to an age where I feel to awkward to discuss my problems with anyone. Just because my destiny's not here now doesn't mean it will never be there.
I feel that you are impatient. Your purpose is something you build up to. It can be a surprise even. Just keep pursuing whatever, and your destiny will unveil itself to you.
You remind me so much of my friend ( He's all philosophical, depressed and troubled. In a way he's inexperienced because he doesn't seem to be trying to get himself out of depression...it seems that he is feeling too sorry for himself and that he feels that he isn't worth anything without that depression.)