Don't waste your time reading this...
I can't say i know - but i feel the, most important thing is the sense of purpose. There is nothing more.
The sense that anything you do is important, that it has an effect on the world.
Anything you do can make you feel like you are adding to your purpose, or that you're taking away from it.
If everything you do is to add to your purpose, you'll feel good about your life. If you do things because you were taught to do them, or you're following a trend, or just for the sake of it, you probably wont feel good about your life.
So if you use this to guide yourself, you are automatically on the right path, and you can't go wrong, there is no way.
On this topic, books you can read about the meaning of life:
The Alchemist
Tuesdays With Morrie
I didn't want to expand on it, because it's something you have to find out for yourself. If you want an example, just go through a day with this in mind.
How do you feel?
That's it.