Most "life planning" advice can be summarized into a single expression: Do what's important now.
It may sound simple, but that doesn't mean it's easy. How often do you think, "I should've handled this differently," or, "I shouldn't be so mean," or, "I should get to know my mom better"-- how many times do you think those thoughts, and yet not do those things? Sometimes the simplest things are the trickiest.
A life of regrets is a bad life. A life of action is a good one. Now just because you act doesn't mean you'll do the right thing-- you'll screw up plenty-- but if you never act, you'll never know, and if you never do, you'll never have a chance. So what if you mess up? Try again. Do it differently-- but don't just give up. If you don't act, nothing will ever get done.
Whether you think you can or can't-- you're right. --Henry Ford
What do you do? As a teen you have a lot of free time, and there are the traditional activities: school, sports, TV, friends, and church. If you're happy with what you have, great, but if not, take a look around. See the suffering in this world: your friends, your family, the hungry, the homeless... Isn't there something you can do?
A lot of times you see an opportunity but you put it off because it would be "too hard" or "too much work." Don't make that mistake. Follow your heart in all you do. Sure, one person can't do it all, but one person can do enough-- enough to make a difference.
The work you do doesn't have to be big to be good. A lot of times you see a huge achievement and think, "Well, I'd like to do something like that, but I'd never have the time." That's not true! No one sits down and does a big achievement all at once. Those that do great things just do little things consistently.
The journey of a thousand miles must begin with a single step. --Lao Tzu
If you have a large task, break it down. Take it day by day. You can't do it all at once anyway, so it's a lot easier to look at what you can do now rather than stare immobilized at the whole thing.
If you live for the future you're going to be unhappy. Live in the now; don't worry about what is to come. You don't decide what happens in life; you decide how you react to it. Be mindful of where you are, make the best choices you can, and always do what you think is right. That is the path to happiness.
In your life, you should feel that you have time to yourself. If you're always busy, that's a problem. What are you doing that you don't need to be? Even if you're only doing things you love, if you feel bad about life you're doing too much. Give something up. Only by letting go will you find the way.
There is a modern idea that being busy is a virtue-- that somehow, when you don't have time for yourself or anybody else, you're doing the right thing. Wrong! Wake up! If you don't have time for yourself or anybody else, why even bother being alive?
Take time to yourself every day. What you do during this time doesn't matter, but set aside at least fifteen minutes daily to collect yourself. Keep a journal, pray, listen to music, meditate-- do what relaxes you. If you work too hard without taking a break, you'll lose sight of who you are and what you should be doing.
What do you want to do when you grow up? Don't know? Neither do I! Questions like that are loaded. You can't determine the future.