A little neglect may breed great mischief mischief, little, breed, great, neglect

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A little neglect may breed great mischief.　　小疏忽酿大祸。
　　Neglect, the action of neglecting忽略；疏忽。The owner’s neglects of repairs to his house房东疏于修理他的房子。
　　Breed,原义是繁殖；生产，在这里引申为产生，导致，相当于lead.
　　Mischief, (formal) damage or harm; wrong-doing(正式)损害；伤害；错事。The storm did a lot of mischief to the crops.暴风雨给农作物造成很大损害。这个词还可以表示调皮；捣蛋；恶作剧。If his parents leave him alone for five minutes, the little boy gets into mischief.只要这个小男孩儿的父母让他单独呆上五分钟，他就会调皮捣蛋。
　　Moral of the sentence：小洞不补，大洞吃苦。