A dog’s life
Definition 1 of 1
Pro Tip 1/3Negative Connotation
This phrase implies a negative quality of life, filled with struggle and discomfort. 
Homeless in the harsh winter, he led a dog's life.
Pro Tip 2/3Avoid Literal Use
The phrase is not about a real dog's life, which can be quite pleasant; it's a metaphor. 
Working three jobs just to make ends meet is truly a dog's life.
Pro Tip 3/3Idiomatic Expression
It's an idiom that may not translate literally in other languages; understand it as a set phrase. 
Ever since the accident, she's been living a dog's life, facing constant rehabilitation.