to lead a dog's life形容人过着贫困潦倒、惨不忍睹的生活；

dog eat dog 残酷、竞争激烈；

dog-tired 筋疲力尽；

sick as a dog病得严重；

His bark is worse than his bite. 刀子嘴、豆腐心；

let sleeping dogs lie 不要自找麻烦、自讨苦吃