The fable is a simple one. A man spends his entire life building a clock made from the finest, sturdiest materials. All the cogs are perfect and practically indestructible. But springs have to be flexible, meaning building them too sturdily would simply not work. Thus the springs could not handle the pressure of the invincible cogs and broke.
The most obvious moral is 'no matter how sturdy an object is, the weakest points can only take so much pressure' and 'denying flaws will only make things worse.'