There is a story in "Book of Han" about a rich man who was a lover of antiques. Among his large collection was a rare vase made of jade. The vase was of exquisite workmanship and of historical value. He loved it dearly.
One night, he noticed a mouse jumped into the vase and was trying to eat some food which the man had carelessly left there. The sight infuriated the man. In a fit of rage, he threw a stone at the mouse. For sure, the mouse was killed, but the precious vase was also broken.
The loss of the vase pained the man greatly. He deeply regretted his own thoughtlessness had brought such unrecoverable loss. He now realized that anyone who only cares for the present and overlooks consequences is apt to bring disasters upon himself. So he sounded a warning: People should not ruin their precious things to get rid of a mouse, but hesitate to pelt a rat for fear of smashing the dishes beside it.
Now, the idiom "tóu shǔ jì qì" is mainly used to refer to people who are cautious in taking action.
tóu shǔ jì qì
投鼠忌器
《汉书》中有这么个故事：有个富人很喜欢古董。在他收藏的很多宝贝中，有一件稀有的玉盂，工艺精湛，具有很高的历史价值，深受这个富人的喜爱。
一天晚上，一只老鼠跳进了这个玉盂，想去吃里边的一些剩菜，正巧被这个富人看到了。他非常恼火，盛怒之下，他拿了块石头砸向老鼠。当然，老鼠是被砸死了，可是那个珍贵的玉盂也被打破了。
这件事使富人非常难过，他深深后悔自己的鲁莽带来的不可挽回的损失。他认识到：只考虑眼前，而忽视后果，将给自己带来灾难。因此，他向世人发出警告：要“投鼠忌器”，不要为了除掉一只老鼠而毁掉自己珍贵的宝物。
现在，成语“投鼠忌器”常用来比喻做事有所顾忌，不敢放手进行。
yǐn láng rù shì
引狼入室
bring the wolf into the house – open the door to a dangerous foe
