该句使用转折结构突出持续行为与外界反应的对比。
Build the dam before the flood comes; sharpen the knife before the wolf arrives.
A wolf lay on the grass, diligently sharpening its teeth. A fox saw this and said, "The weather is so beautiful, and everyone is resting and having fun. Why don't you join us?"
The wolf did not respond, but continued to sharpen its teeth, making them incredibly sharp and keen.
The fox asked curiously, "The forest is so quiet; the hunters and hounds have gone home, and there are no tigers prowling nearby. Since there is no danger at all, why are you working so hard to sharpen your teeth?"
The wolf stopped and replied, "I am not sharpening my teeth for entertainment. Think about it: if one day I am chased by hunters or tigers, it will be too late to sharpen them then. If I sharpen them now, I can protect myself when the time comes."
One should prepare for a rainy day and be vigilant in times of peace, so that when danger strikes unexpectedly, one will not be caught in a state of panic.
"One regrets the lack of books when they are needed"; if one does not enrich their knowledge during normal times, trying to "grab Buddha's feet at the last minute" will be too late.
Some people complain about a lack of opportunities, but when the chance for promotion actually arrives, they lament that they haven't accumulated enough knowledge and ability to handle it, leaving them with nothing but regret.
洪水未到先筑堤，豺狼未来先磨刀。
一只野狼卧在草地上勤奋地磨着牙。狐狸路过，见状便说：“天气这么好，大家都在休息娱乐，你也加入我们吧！”
野狼没有理会，只是继续磨牙，让牙齿变得又尖又利。
狐狸感到很奇怪，问道：“森林里如此安静，猎人和猎狗都回家了，老虎也不在附近徘徊，既然没有任何危险，你又何必如此卖力地磨牙呢？”
野狼停下动作回答道：“我磨牙并非为了娱乐。试想，如果有一天我被猎人或老虎追逐，到那时想磨牙也来不及了。若平时就把牙齿磨好，危机来临时就能保护自己了。”
做事应当未雨绸缪，居安思危，这样在危险突如其来时，才不至于手忙脚乱。
“书到用时方恨少”，如果平时不充实学问，等到关键时刻才临时抱佛脚，往往已为时已晚。
也有人抱怨机遇不够，然而当升迁的机会真正降临时，才感叹平时没有积攒足够的知识与能力，导致无法胜任，到那时也只能后悔莫及。