In Chinese, people express modesty by saying that they gave all their knowledge back to the teacher. This implies that the person never really owned the knowledge in the first place, but simply borrowed it from the teacher to pass the exam. But it also implies that the person never cherished this knowledge, because he or she never owned it, and so they neglected it and eventually forgot it. It's just like the difference between living in a dormitory and living in your own house. No one who lives in a dorm takes very good care of it, especially the public areas. But once you own a home, you make it beautiful and keep it clean because it has greater value to you. This is pride of ownership, and what is owned is cherished. What is cherished endures.
As much as Chinese students appreciate their foreign teachers, they should not forget that responsibility for learning comes from within, not from without. The teacher cannot "give" someone English. No one can "get" English from a teacher or from a book like one can get a cold. Responsibility for learning can only come from the learner, when he or she freely chooses to own the quality of his or her learning experience, versus relying on borrowed knowledge from experts.