業精於勤，荒於嬉 [业－于－－－于－]

Jyutping jip6 zing1 jyu1 kan4 ， fong1 jyu1 hei1
Pinyin yè jīng yú qín ， huāng yú xī

Definitions (Wiktionary)
  1. proverb
    academic excellence is achieved through diligence, while studies are neglected and deteriorate when one frolics