For example, if there were no dogs, how could people complain about leading a dog's life?

例如，如果没有狗的话，人们又怎么能说生活得连狗都不如？

Tony was once a docker, and led a dog's life.

托尼原来是个码头工人，过着受折磨的日子。

One worked on a lighter and led a dog's life while the other led a light-hearted life.

一个在一条驳船上工作，过着牛马不如的生活。另一个过着轻松无虑的生活。