The teacher says,

It’s difficult to absorb a waterfall when your cup is too full. What kind of cup can hold a waterfall even if it was empty you might say? The cup is your brain, which when not too full of itself, can hold waterfalls of information and knowledge. However, when that cup feels too full and closes off to outside feedback, it can no longer contain a single drop of new knowledge or self-reflection.

Yu-kai Chou