My wife once asked me how I could practice the same piano piece over and over and over, for hours, without being bored. It seemed to her that I was making a great effort. To me, every time I play, I discover something new, about music, about myself, about the instrument.... Even the least interesting basic exercise piece like Hanon (which roughly corresponds to the sit-up or squatting to build your body), if I concentrate on how every parts of my body works to interact with the piano, it's an unlimited source of discovery. I wish I'd known that when I was younger and taking lessons---I discover how to enjoy practicing long after I stop taking lessons.