At some point the work inevitably becomes difficult, heartbreakingly so. If it didn't then it wouldn't be work, it would just be a pastime, a hobby. Most students, at this point, either give up or, worse still, use the force of their ego to constantly drag the work back into familiar territory every time it threatens. Soon they become such experts at this that the teacher stops correcting them – effectively stops teaching – a situation that is far worse for the teacher than it is for the student who has effectively turned the tables. Those that refuse such manipulations (which are always conscious) continue the work with redoubled effort. When the going gets tough the tough get going.