This famous koan tells the story of a professor of zen Buddhism that visited a zen master, and after listening to the professor's impressive intellectual knowledge the master served tea. When the visitor's cup was full, the master kept pouring. Tea started spilling out of the cup and over the table.
"The cup is full!" cried out the professor.
"Like this cup," said the master, "you are full of your own opinions and speculations. How can I show you zen if you don't first empty your cup?"
When our minds are full and clouded with opinions and assumptions about everything, it is difficult to learn new things, to dare to challenge our own beliefs. Cultivate self-awareness and learn to see things as they are not to create too many assumptions. Create space for new things in your life.
“In the beginners mind there are many possibilities but in the experts there are few.” Suzuki Roshi
And remember Ackoff: It is always better to do the right things wrong than to do the wrong things right.