When practicing pieces of music on either the guitar or piano, I have almost always noticed the following pattern: to start with, each practicing session is better than the previous. However, there comes a time, possibly when I am limited from further improvement by lack of techique, that my playing starts regressing. My performance of the piece I have been studying becomes sloppier as if I have partly lost what I had previously conquered.
Have you come accross that pattern on yourselves, your peers, your students? Or is it just my practicing routine? Are there any suggestions on how I could prevent this regression and maintain an improvement, such that each time I play a piece, I at least play it as well as during my previous practicing session?
Background info: I am an amateur musician, without any formal (i.e., in a music conservatory) music training.