I can't find it anywhere in "NTC's American Idioms Dictionary" or online.
If I was to guess what it would mean; if you said, "You have the life of a boiled fish."
I would say it means:
You have no life. ~This is another Idiom; since, it is impossible to not have a life.
In my opinion, you don't have a life worth living. ~This is basically what someone means when they say, "You have no life."
You have a painful life. ~Depending on if the fish is still alive or not....
Your life is tragic.
You have a hard life.
Idioms are another way for people to feel special. They allow us to create or say something, that not everyone can decipher. We are free to do whatever we want; so it is a choice between: being easily understood or feeling special.