On the very first day of the world, God created the cow. He said to the cow:

Ah Gu (cow), today I have created you!
Your job is to go to the field with the farmer all day long. You will provide the energy to pull things!
You will also provide milk for people to drink!
You are to work all day under the sun! In return, you will only eat grass. For that, you will have a life span of 50 years."
Ah Gu objected.
What, I work all day in the sun and I get only to eat grass!
On top of that, I have to give my milk away!
This is tough and you want me to live 50 years! I'll take 20 and you can have the remaining 30 years back!" God agreed.

On the next day, God created the dog.
He said to the dog:
Ah Kow (dog), I have created you for a purpose.
You are to sit all day by the door of your master's house!
Should anyone come in, you are to bark at them!
In return, you will eat your master's leftovers.
I'll give you a life span of 20 years."
Ah Kow objected.
What!
I have to sit by the door all day and will need to bark at people, and what do I get...LEFTOVERS...

This isn't right, I'll take 10 and you can have the remaining 10 years back!"
God agreed again.

On the third day, God created the monkey.
He said to the monkey.
Lao Kao (monkey), your job is to entertain people.
You will make them laugh, act stupid and make faces!
You will also do somersaults and swing on trees to amaze them.
In return, you will get to eat bananas and peanuts.
For that, I'll give you 20 years to live."
Naturally the monkey objected.
This is ridiculous,
I gotta make faces and make people laugh let not even come to the part about the trees and somersaults.
Tell you what, I'll give 10 years of my life to thank you for my existence and I'll take 10.
What do you think?
God agreed again.

On the forth day, God created humans.
God said to the man.

You r my best piece of work, for that, u will only need to sleep, eat, sleep, play, eat, sleep again & do nothing else. You'll get to eat all da best things & play with the best toys.
All u need to do is enjoy all ur life.
For this kinda of life, I'll give u 20 years."
Just like da rest, da man objected.
What, all I need to do is relaxed & enjoy myself and I've only 20 years to live?
Tell u what, u've 30 years back from Ah Gu, 10 years from Ah Kow & another 10 from Lao Kao & u probably don't know what to do with all those lives. Why not I take them all and I'll have 70 years to live?" God being such good natured, agreed with a smile.

AND THAT IS WHY,
We eat, sleep, play & enjoy for da first 20 years of our lives when we r growing up.
Work like a cow for da next 30 to raise our family.
Sit outside da door & bark at people for da next 10 when we r retired.
And finally, we make faces & perform monkey tricks to entertain our grandchildren for da final 10 years.

GET IT????