This is a common saying and a commonly told story in martial arts circles ...
A master was trying to explain something to a student. Now this student was not a brand new student, but a senior student who had learned many things. He had knowledge and experience aplenty to draw upon. But each time the master tried to explain something new to the student, the student kept trying to hold it up against his own notions of the way the world is and how it ought be, and he was unable to see the lessons in what the master was trying to teach him.
Finally, the master poured a full serving of tea into his own cup, and into the cup of the student. Then he told the student he wanted to give to him some of the tea from his own cup. He began pouring tea from his cup into the student's cup, but the student's cup was already full, and all the tea from the master's cup spilled out over the cup onto the surface below.
The student said, "Master, you can't pour anything into my cup until I empty it to make room for what you are trying to give me.", and the master replied "Yes I know." "And I can't give you any new thoughts or ideas or perspectives on life's lessons until you clear out some thoughts that are already teeming in your mind to make room for what I have to teach you." Then the master paused for a brief moment, meeting the student's eyes with his own knowing look and calmly but sternly said: " If you truly seek understanding, then first, empty your cup!"
The student pondered for a moment with a look of absolute bewilderment. Then a look of enlightenment came over him, followed by a smile, and a look of receptiveness. The master started to explain again, and this time the student saw what the master was trying to say.
See HindrancesToLearning, BeginnersMindCategoryStory, CategoryEasternThought