A single leaf obscures one's eyes
To be unable to see the true origin of the problem or the situation as a whole because a part of the problem is particularly perplexing
Negative
对世界形势要做全面的分析，不要一叶障目，不见泰山 | Duì shìjiè xíngshì yào zuò quánmiàn de fēnxī, bù yào yīyèzhàngmù, bù jiàn tàishān
You must analyze the state of the world as a whole, not get focused on one small issue
[Source]
你们这样做，是一叶障目，结果肯定会达不到预期的 | Nǐmen zhèyàng zuò, shì yīyèzhàngmù, jiéguǒ kěndìng huì dá bù dào yùqí de
None of you are seeing the forest for the trees [by approaching the issue like this], and you will definitely not achieve your expected results
[Source]
To be unable to see the forest for the trees
一叶蔽目 (yī yè bì mù)
一叶障目，不见泰山 (yī yè zhàng mù, bù jiàn tài shān)
None
《鹖冠子》(Hé Guān Zǐ), an eponymous work from the Warring States Period (战国时期 | zhàn guó shí qī | 475 - 221 BC). The work itself is the compilation of multiple authors' writings on several schools of thought, particularly that of Huang Lao (黄老). It is known in English as the "Pheasant Cap Master."
In the state of Chǔ (楚国, 770 - 223 BC), there lived a very poor scholar who wanted to find a way to become wealthy.
One day, he was reading a book, and he encountered a line which said, "Anyone who obtains the leaf that a grasshopper uses to conceal its body when it hunts cicadas will become invisible." He instantly believed this to be true, and he went outside to find this special leaf.
After long searching, he finally managed to find his quarry. He thrust his hand out to seize the leaf, but in his excitement, it fell and mixed in with the leaves already covering the ground. Not entirely certain as to which leaf was the one granting powers of invisibility, he decided to take all of them home and test them out one by one.
When he arrived at home, he hunted down his wife and held the first of the leaves in front of his eyes. "Can you see me?" he asked earnestly.
"Yes," she replied.
And so this went for countless leaves, until the wife lost her patience. The next time her husband asked whether he was visible, she lied, "No, I can't see you!"
The scholar was ecstatic, and he ran outside with his leaf and started stealing objects right in front of their owners.
Almost immediately he was apprehended and hauled before a baffled county magistrate. He explained himself, and the magistrate couldn't help but laugh. The foolish scholar was released and allowed to return home