In some forms of Zen training, the student
is given a koan. A koan is a question or a story that is puzzling
in some way. For example, "What is the sound of one hand
clapping?" The discipline is to stay with the koan until
you "get" it. Sometimes this takes months, even years.
When the students are monks and live in
a monastery, they stay with the koan while they eat, sleep, cook,
clean, and also they spend time in intense periods several times
a day doing nothing but hanging out with that koan (this is known
as zazen, or sitting meditation).
The student stays with the koan intensely,
wrestling with it, fighting with it, trying to look at it from
different angles, trying to "figure it out," allowing
it to be there, and so on. Intensely. They say it's like
swallowing the moon which then gets stuck half way down. The
frustration can stay at a high pitch for a long time.
And then something happens. The student
gets it. Often this is a full-blown "awakening"
and the student is never the same again.