Be kind and good and moral.
This is the most important thing. Be the type of person who people remember as good and kind. You will never look back on your life and regret a decision that was the good and kind thing to do. Every minute of every day the only person who you have to live with is yourself. Make choices that you can look in the mirror and be proud of. Being good and kind does not mean you don't stand up for yourself, or that you are someone people can walk all over. It means appreciating little things, like when someone you care about does something to show they think about you when your not around or when a stranger holds the door for you. It means making dinner for your wife someday after she had a long day at work. Or calling your mother out of the blue just to tell her you love her. Kindness is not just the acts that you do, its the thoughts you have in your head. Not gossiping about someone who isn't there. Not making fun of someone even though all your friends are. Standing up for what is right, even when you will never get credit for your good deeds. Being kind and good is the most important thing you can be.
Learn from everyone and everything.
Learn from the smart people, learn from people you hate, learn from animals, learn from books, learn from TV, learn from the internet. Learn at school, learn while you are standing alone. Seek out things to learn, not just school or education, but common sense. Learn things you think you will never need to know. Ask questions about everything from everyone! Take every opportunity to learn. Learn to fix your car, build a house, learn about wars and history. Learn why we are all made of start dust and how the universe is all made of math. Learn why someones has the opposite opinion of you. Learn why sometimes its ok to ugly cry. Learn why gravity isn't the problem when you fall, but the ground when you hit it. Don't be afraid to look stupid! Your dumber when you don't know, but try and pretend you do. Allow people and things to teach you, ask to be taught.
Be strong. Strong of mind, strong of will, strong of heart, and strong of body
Be strong of mind. A strong mind will get you places others only dream of. It allows you to speak with intelligence while others stand there looking foolish. A strong mind will attract others and will allow you to grow in directions you never thought possible.
Be strong of will. A strong willed person isn't bad thing. Your willpower is what will get you over the hardest times of your life and it will get you to the peak of the best times. It will get you to the end of the 5k run, it will get you to work on days you want to stay in bed, and it will get you through the heart break of choosing the best thing for your sick pet. You willpower will overcome your fears, like a fear of heights, or a fear of being alone. And your willpower will get you past being average and get you through the challenges the world will throw at you.
Be strong of heart. You will have heartbreak in your life, its the hardest thing that will happen to you. I don't just mean death or breakups, although that will happen too. I mean your heart will be broken by disappointment and intentions too. The people you love the most may do it to you. People are not perfect, and sometimes the people you thought highly of, turn out to be the greatest disappointment. A strong heart will allow you to move past these things. Sometimes it will mean leaving someone or something you love behind. Or it will give you the heart to forgive them. Your heart needs the protection that only being strong can give it.
Be strong of body. Go to the gym! Lift weights! Go for a hike or a run! It will keep you healthy and it will help keep you happy too. You will need to cope with all the wildness of life. A strong body will help you keep up physically and it will give you a method of dealing with things that are hard.