Thanks to Daryl at Anecdote for this.
While the master quietly served tea the professor talked about wanting to learn Zen. The master poured the visitor’s cup to the brim, and then kept pouring. The professor watched the overflowing cup until he could no longer restrain himself. “It’s overfill! No more will go in!” the professor blurted. “You are like this cup,” said the master.
There’s something rather valuable about the quality of receptiveness, and for some of us it’s worth practicing.