[hilbert42]

That's very good advice if one's well disciplined. The trouble is many of are not and it's why we need a good teacher to keep us on the straight-and-narrow.

My teacher was forever nagging me to "play what's written, not my interpretation of it". She'd also tell me to "go home and practice the actual lesson", boring Czerny scales or such, "...and not muck around and waste time playing songbook stuff that I liked the sound of".

[mtalantikite]

Right now I’m working with a jazz/improvisation teacher and he has me play through a piece once strictly as it’s written, once again strictly but singing the melody, and then the third time through with improvisation on the melody. Sheet music is thrown away as soon as possible. Of course jazz compositions are much shorter than classical pieces, but I do think the premise of getting it down strictly and slowly opening it up is a great way to practice.