Jyutping
zi6 ji5 wai4 dak1 gai3
Pinyin
zì yǐ wéi dé jì
Definitions (Wiktionary)
phrase, idiomatic
To mistakenly think that one will ultimately succeed as the result of having accomplished only part of one's plan; because you won a single battle, you mistakenly think you will win the war.
一切狡猾的人，不照科學態度辦事的人，自以為得計，自以為很聰明，其實都是最蠢的，都是沒有好結果的。
一切狡猾的人，不照科学态度办事的人，自以为得计，自以为很聪明，其实都是最蠢的，都是没有好结果的。
yī qiè jiǎo huá de rén ， bù zhào kē xué tài dù bàn shì de rén ， zì yǐ wéi dé jì ， zì yǐ wéi hěn cōng míng ， qí shí dōu shì zuì chǔn de ， dōu shì méi yǒu hǎo jié guǒ de ． All sly people, all those who do not have a scientific attitude in their work, fancy themselves resourceful and clever, but in fact they are most stupid and will come to no good.
Examples (Wiktionary)
Mandarin
一切狡猾的人，不照科学态度办事的人，自以为得计，自以为很聪明，其实都是最蠢的，都是没有好结果的。
一切狡猾的人，不照科學態度辦事的人，自以為得計，自以為很聰明，其實都是最蠢的，都是沒有好結果的。
yī qiè jiǎo huá de rén ， bù zhào kē xué tài dù bàn shì de rén ， zì yǐ wéi dé jì ， zì yǐ wéi hěn cōng míng ， qí shí dōu shì zuì chǔn de ， dōu shì méi yǒu hǎo jié guǒ de ．
All sly people, all those who do not have a scientific attitude in their work, fancy themselves resourceful and clever, but in fact they are most stupid and will come to no good.