I'm realizing more and more that most people, myself included, seem to live most of their lives completely backwards. So much time and effort is put towards achieving goals that haven't really been defined, or are vague enough that they shouldn't even be referred to as "goals".
Define your goals
If you don't know what you want, or what you're working towards, you'll never get there. You have to figure out where you want to be rather than trying to figure out what to do to chase down the ellusive goal of happiness or contentment. It's only once you have the goal in mind that you can start taking steps to get there.
Without knowing your goals, it's like you're running in a race where you can't see any of the other runners, and you have no idea where the goal is – for all you know, you could have reached the end of the race a long time ago, but you had no idea that that was where you wanted to stop.
Setting goals like "I want to be an olympic swimmer by the end of the month" just doesn't work. Even attempting something that's unrealistic will just leave you frustrated and deter you in the future. Know yourself, know your strengths.
Know your limits
It's important to know your strengths and utilize them, taking advantage of anything you have that may get you ahead. But even more important is to realize your limits – and not accept them. If something is going to hold you back from your goal, that something needs to be overcome.
Don't give up
Life is really good (really really really good) at throwing you curveballs when you least need or expect them. Don't let these cause you to lose sight of the ultimate goal. Each hardship just makes you appreciate everything that much more when you finally get where you're going.
Don't forget about the others…
Everyone else is (more or less) in the same position as you. Don't knock other people down to get ahead. Destroying other people's goals will just make reaching yours seem less fulfilling and leave you feeling like you're missing something. Treat people the way you want them to treat you. If you treat people like crap, or crush them physically/financially/emotionally – it will come back to haunt you.