when things reach an extreme, they can only move in the opposite direction (idiom)
Definitions (粵典–words.hk)
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Definitions (Wiktionary)
phrase, idiomatic
A thing turns into its opposite if pushed too far; Once a certain limit is reached, a change in the opposite direction is inevitable.
不要總是批評學生,否則,物極必反。
不要总是批评学生,否则,物极必反。
bù yào zǒng shì pī píng xué shēng , fǒu zé , wù jí bì fǎn . Don't criticize the students or it may backfire on you.