I understand. I do. I feel this all the time and have for a long time.
But you're nineteen, and no, you didn't waste those years--you spent them growing up. That's allowed. Just because a very small percentage of other people do something big in that time, doesn't mean you're mediocre if you don't.
Besides, your brain isn't even done developing yet and won't for another five or six years.
Now, what is the impact you want to make? What is it that you are called to do? What, in all its specificity, is your vision?