I practice an hour a day, but I find that learning pieces (eg. a sonata) takes a long time.I find myself practicing the parts that I have already got reasonably accurate, instead of working on new stuff. How do I stop myself from doing this?
One becomes pleased with the progress, dwelling on it, rather than moving on to the really hard bits.
This is the tendency in one's overall progress; both personal and pianistically. Accomplishing a certain amount, reaching certain goals and then sitting back and becomimg complacent, ignoring the really hard work that must be done in order to become a truly great artist.