我非沉鱼亦非落雁
[wŏ fēi chén yú yì fēi luò yàn]
This translates as 'I Am Not the One Who Makes Fish Sink or Geese Fall', coming from two idioms - “沉鱼“ (fish sink because they're dazzled while swimming) and ”落雁“(goose fall for its beauty). It means the user does not claim to possess such astonishing looks but is comfortable with ordinary appearance or character.