As Einstein, who allegedly said this, discovered: the theory of relativity, proved atoms existed, and E=mc2, most people classified him as a genius(Periodic Sentence). Einstein was a genius of academics; he was more acquainted with the way his brain worked, especially compared to that of many of us (Parallelism). So he took what he needed to know (From i.e. teachers, mentors, or parents), in order to make his life more like he wanted it to be. Another individual that most classify as a genius is Wolfgang Amadeus Mozart, a music composer that started when he was just the age of 5 years old (Appositive). Mozart was known as a child prodigy in music, he is well known for many symphonies and operas such as, Don Giovanni, The Magic Flute, and the Jupiter symphony. From the beginning, he was aware exactly what he had a passion to do, to play music, and that is exactly what he did.
Most of mankind classifies this group of prodigies as geniuses because of what they did in order to make the world a different and changed place, but I believe they are geniuses because of what they did for themselves, in order to make their lives happier for their own desire. If you really think about it, what most people want from life is happiness; to be able to push through all the struggles and come out as a better person; to fight for what you want or in what you believe; somebody who controls their life, in order to make it a happy