I taught beginning band for over twenty years and I was often asked how I could stand to listen to the sounds beginning players make day in and day out. My response was always the same. I told them I only hear the "progress" of the group because that is what I focus on. My advice to anyone learning to play a musical instrument is to do the same. I have never met a musician at any level who is entirely satisfied with how well they play. They are always listening for areas where they can improve. I'm sure they know as I do that once one is completely satisfied that's when the growth stops.