For want of a nail the shoe is lost; For want of a shoe the house is lost; For want of a horse the rider is lost.

• 因为少了一颗钉子而丢了马蹄铁；因为少了一只马蹄铁而损失了战马；因为少了一匹战马而损失了骑手。（千里之堤，溃于蚁穴。）