But there are just five things that I cannot do in your place.

From Novice to Master An Ongoing Lesson in the Extent of My Own Stupidity by Soko Morinaga.

A while ago I gave a public lecture at a university.  The speaker who preceded me talked for about an hour and a half, running over his allotted time.  The break period between our talks was shortened, and I was called to the podium right away.  Concerned for the audience, I opened by asking, "Did you all have time to urinate?”

Apparently this was not what the audience had expected to hear.  Perhaps they were particularly surprised because the person standing before them, talking about pissing, was a monk.  Everyone broke into hearty laughter.

Having started out on this note, I continued to press on. "Pissing is something that no one else can do for you.  Only you can piss for yourself."  This really broke them up, and they laughed even harder.

But you must realize that to say, “You have to piss for yourself; nobody else can piss for you” is to make an utterly serious statement.

Long ago in China, there was a monk called Ken.  During his training years, he practiced in the monastery of Th-hui, but despite his prodigious efforts, he had not attained enlightenment.  One day Ken's master ordered him to carry a letter to the far-off land of Ch’ang-sha.  This  journey, roundtrip, could easily take half a year. The monk Ken thought, "I don't have forever to stay in this hall practicing!  Who’s got time to go on an errand like this?"  He consulted one of his seniors, the monk Genjoza, about the matter.

Genjoza laughed when he heard Ken's predicament.  “Even while traveling you can still practice Zen!  In fact, I'll come along with you,”—and before long the two monks set out on their journey.

Then one day while the two were traveling, the younger monk suddenly broke into tears.  “I have been practicing for many years, and I still haven't been able to attain anything.  Now, here I am roaming around the country on this trip; there’s no way I am going to attain enlightenment this way," Ken lamented.

When he heard this, Genjoza, thrusting all his strength into his words, put himself at the junior monk’s disposal: "I will take care of anything that I can take care of for you on this trip," he said. “But there are just five things that I cannot do in your place.

“I can't wear clothes for you. I can’t eat for you. I can't shit for you. I can't piss for you. And I can't carry your body around and live your life for you."

It is said that upon hearing these words, the monk Ken suddenly awakened from his deluded dream and attained a great enlightenment, a great satori.