Maybe not the most transformational advice, but effective: A professor who was into the contemporary/progressive music scene during my college years used to hear me practicing lots of Schubert, Chopin, Liszt, etc. finally burst into my practice room and, after briefly complimenting me, asked, "why in the hell are you still playing "Mary Had a Little Lamb"? That set me on a voyage of discovering and developing a more adventuresome repertoire.