And who's to say that we're not good enough?

Does everyone have a purpose in life? And if so, does everyone realize and strive to reach it? If everyone is trying to be the best they can be and change the world, why are there so many problems?

I guess I am confused. I mean, I'm 20 years old and I want to change the world...or at least make a significant contribution. Do other people feel that way? I find myself wanting to walk away and tell everyone:

"Just watch what I'm going to be. Watch what I'm going to do. I don't know what it is yet, but it will be huge; it will be fantastic. Just you watch!"

What scares me is the thought of failure. What if I can't? What if I'm not good enough, not smart enough, not talented enough, not aware enough, just not enough? What if I go through life trying to find my purpose just to realize I don't have one...will that happen? What if I am stuck waiting for my life to start and to be happy and that doesn't happen?

I know the stereotype. The youg college student thinking the world is their oyster and that they will be the one to change it and make it a better place. They wind up thinking that until they realize they are now old, gray, and cynical. Then they laugh at the foolishness of the younger, hopeful generation. I don't want to be like that. I want to make a difference. I want to look back and say "Wow, I did something good. I did it right."

Then I wonder if I want to achieve this sense of purpose because I want to do something...or because I want to show people that I can. Do I want to do something great just to show that I can? Do I want to say to those that hurt me

"See what you left? I can do amazing things. Do you regret hurting me? Do you see what you missed out on? You could have been a part of this. You could have helped me achieve this, but you didn't. That is what you get."

I'd like to think I just want to do somethin amazing and that I'm not a vindictive person...but I think it is a mix of both. I think it's human nature to want to show off for people who have hurt you. I think I want to do something great and I want to show it off to those who have hurt me.
I don't know where this all came from. I think I'm scared that I will never be good enough to do something amazing or to make the world a better place.