Poems are taken from the Soviet textbook of English for children. They can also be easily found on the English version of Wikipedia.
How insignificant actions can lead to unpredictable results. Useful not only for children.
Who Was the Kingdom Lost?
For want of a nail
the shoe was lost,
For want of the horse
the rider was lost,
For want of the rider
the battle was lost,
For want of the battle
the kingdom was lost,
And all for the want
of a horse-shoe nail.