Yanamino冰冻三尺，非一日之寒
bīng dòng sān chǐ , fēi yī rì zhī hánbingdongsanchi,feiyirizhihan
- three feet of ice does not form in a single day (idiom); Rome wasn't built in a day
Data from JMdict, KANJIDIC2 (EDRDG), KanjiVG, CC-CEDICT and Make Me a Hanzi. Sources and licences