Teaching has helped me the most.It forced me to analyse consciously the way I was playing so that I could explain it to the student. It brought into my awareness the fact that many of the wrong things/bad habits I detect on the student, I also had, so it made me clean up my act.Many times (especially with little children), some movements they made spontaneously provided elegant solutions to technical problems I had been struggling with.Next I would say the practice of martial arts and yoga because they taught me how to use my body efficiently and properly.Modern technology: CDs with most of the piano repertory played by different pianists; notation software that allow you to write music and hear what it sounds like; digital pianos that allow you different sounds and recording facilities (on mine you can record right and left hand on different tracks, for instance); the net (pianoforum) (Unfortunately most of this was unavailable when I was a student).My own teachers, some of which keep teaching me everyday, even though they have passed away many years ago.Best wishes,Bernhard.