Some goal or function, perhaps? Some all-encompassing ideal that we can all strive for?
Since the dawn of civilization, most of man's greatest achievements (as well as our most horrific acts) have been driven by our desire to conquer the world. Now in the 21st century, I think it's fair to say that we have managed to more or less take full ownership of the globe; none the least in our attitudes to our natural resources.
Congrats people, the goal of the last nineteen centuries has been accomplished; the last of the blank corners of the map have been explored and filled. The beginning of the 20th century saw the consolidation of these powers grasping for control of the world; which culminated in multiple wars, 2 of which were global, and technological advances primarily in the area of weaponry.
Now in the 21st century, we are what Sociologists call "globalized". We are no longer fragmented nations, separated by culture and language. We are connected, all throughout the world, now more than ever by the internet.
The world is changing, and humanity is being called upon to change along with it. The choices that we, especially the young people, make will decide whether things will change for the better or the worse.
You want a meaning in life? In the next century, with the final drops of oil being pulled out of the earth, this world is either about to dissolve into chaos and anarchy or be created into a paradise by the brilliant and ingenuitive. We will soon find ourselves in a world where a person's merit is not judged based on looks or class or wealth. It will be judged based on what you can do for those around you.
Start learning about everything you possibly can. If the worst does occur, it's people with a wealth of knowledge who will have the most influence in the world. Our first task as a species was to become masters of this planet, now we face an even greater task: continue to live here without destroying ourselves.