Believe it or not, I've heard many pianists my age and older who were formally trained since they were little kids and their level is just a disappointment for all the years they spent on the instrument (10+). However this is what I learned: They were encouraged by their parents to play piano while they didn't really feel it, and because they didn't have that much interest they didn't practice a lot in the past 10 years, in fact they would tell me that they practiced 30-45 minutes every other day!
I never really remember why I took the decision to play piano, I just went straight up to my father when I was 12 asking for piano lessons, I felt a deep urge to hit those black and white keys. We didn't have a piano at home and we didn't really understand the difference between a $100 electronic Casio keyboard and a $3000 upright piano, of course I got to play the Casio for the first three years, and because we could never find a good teacher and I couldn't learn anything more serious than playing songs by ear I had to do something to satisfy my musical desires.. And so was it, I composed my first pieces before hearing any classical piece in my life. I live in Egypt so Western classical music is rarely played anywhere. In fact, I was never fully aware of its existence -I would hear stories of Beethoven's deafness though- before I turned 15. It was about that time that a professional musician heard me play a composition of mine and insisted I start taking formal piano lessons. Before I knew it, I fell in love with classical music, and the love hate relationship started.
Piano giants who entered history have much interesting stories. Franz Liszt, the famous Hungarian virtuoso who was accompanied by the term "Lisztomania" for his dazzling pianism. He was very well known for his stunning sight reading abilities. He could go through a whole symphony playing most if not all its parts/instruments on piano. He once sight read Chopin Etudes Op.25 that Chopin himself wished he could play it as beautifully. When asked how he does it, he replied that it comes with daily practice, 8 hours per day dedicated to nothing but sight reading. I think it's that amount of dedication that engraved his name in the history of music for centuries..
Another great pianist was the Russian-born Sergei Rachmaninoff. His technique was outstanding that a wrong note was an extremely rare event in his recitals. He was also a great composer of the Romantic period. It was once reported that he practiced 15 hours per day to sharpen his skills and even surpass his own limits, in an attempt to gain the tonal clarity of his contemporary J.Hofmann.
It's obvious that talent alone isn't what brought these guys such fame and legendary status. It was their dedication, tireless practice and most importantly their incredible love for music. If you love music that much, you will fight for it, and if you do, it will reward you greatly.