物极必反

when things reach an extreme, they can only move in the opposite direction (idiom)

thing / object / matter / abbr. for physics 物理

extremely / pole (geography, physics) / utmost / top

certainly / must / will / necessarily

contrary / in reverse / inside out or upside down / to reverse / to return / to oppose / opposite / against / anti- / to rebel / to use analogy / instead / abbr. for 反切[fan3 qie4] phonetic system