Usually, to become a great graphic designer, you need to have
a passion for it - a strong interest in all elements of design.
You can learn the processes, and bang out some fair designs,
but just like a musician or any other creative, you need to be
completely absorbed in it and have an aptitude for it in order
to be great at it.
Speaking for myself, in the past, I used to draw logos and
cartoons when I was supposed to be using the Study Hall
period in school for doing my homework. Then, in the early
1990's when I got my first computer, it was a no-brainer
to transfer my real world passion for graphic design to
the virtual environment.
Cheers! - "Wiz"