用心良苦 yòng xīn liáng kǔ

DEFINITIONS

  1. to ponder earnestly
  2. to give a lot of thought to sth

CHARACTERS

用 yòng use, employ, apply, operate; use
心 xīn heart; mind, intelligence; soul
良 liáng good, virtuous, respectable
苦 kǔ bitter; hardship, suffering