It took me 40 years to find this poem. I read the original
in the 1960's then misplaced it. After searching all over,
the original was found in 2001 under some personal papers of mine.
This is so true and points out that no one is indispensable.

The Water Cure

Sometime when you're feeling important

Sometime when your ego's in bloom

Sometime when you take it for granted

You're the best qualified in the room.

Sometimes when you feel your going

Would leave an unfillable hole

Just follow this simple instruction

And see how it humbles your soul.

Take a bucket and fill it with water

Put your hand in -- up to your wrist

Take it out -- and the hole that's remaining

Is a measure of how you'll be missed.

You can splash all you please as you enter

You can stir up the water galore

But STOP -- and you'll find in a minute

That it looks quite the same as before.

There's a moral in this quaint example

Just do the best that you can

Be proud of yourself but remember

There is no indispensable man.