Friends:

Precious yet often wasted is this Human Opportunity!

The Blessed Gotama Buddha once explained:
Bhikkhus & friends, imagine a single floating ring drifting in the great oceans!
Imagine also a blind turtle, which surfaces only once every hundred years...
What do you think, Bhikkhus, would that blind turtle by chance often dive
right up under this randomly drifting single ring & insert its neck in the hole?
If it ever would at all, Sir, it would only happen after an incredibly long time!
Yet, Bhikkhus & friends, I tell you, that this would happen sooner, than a fool,
who has fallen into the lower worlds would again regain this rare human state...
Why so? Because down there exists neither behaviour guided by the Dhamma,
nor any honesty, nor any morality, nor any good doing or meritorious activity...
There prevails only this evil: beat or be beaten, eat or be eaten, cruel merciless
killing and voraciously swallowing up of any weak. Why is it so primitive there?
Because, Bhikkhus, there nobody have seen these 4 Noble Truths! What four?
All this is Suffering; This Greedy Craving is the sole Cause of all Suffering;
No Craving is the End of Suffering; The Noble 8-fold Way Ends all Suffering,
Therefore should an effort be made NOW to understand the 4 Noble Truths!

Comment:
Despite the fact that downfall is a common event occurring at most deaths
(>97%) many beings think that the downfall either not happen to them (sic!),
or that it does not exist at all... They cannot remember the last nasty surprise...
Learning anything about cause and effect is thus effectively disabled!
The very same mistakes are thus repeated, life after life, almost endlessly!

 

The Blind Sea-Turtle Simile...
 
Source (edited extract):
The Grouped Sayings of the Buddha. Samyutta Nikāya. [V:455-6]
section 56: Saccasamyutta. Thread 47: The Ring and Blind Turtle ...