Obviously a good instructor should not let a student's bad habits get to him/her but as been said we are human!
There is however a minority of students who seem to expect the instructor to do all the work. It's as though they don't really understand the nature of learning and the "rules" of the game. Dare I say it but some of this may have come from the new culture of education that everything has to be easy. Let's face the fact that the average student is going to find bits of the syllabus challenging and that they should not expect to improve with every lesson so long as they have learned something new.
My feeling is that to a broad extent instructors are facilitators (particularly as the student progresses in learning) and that we are there to mirror back to the student how to solve his own problems and take ownership of command,