working like a dog
Busting your balls is an idiom that means working very hard at something.
"Hit the books."
hard working
it means that
Life Is Sometimes Hard
No, if something is "like" something else, it is a simile.
more hard-working, most hard-working
It's not an idiom. "Fruits" means the end result of something, so "fruits of labor" would be what you earned from hard work.
Hard nosed
The idiom "a nut to crack" has the basic meaning of "a problem to solve." Some "nuts" are hard to "crack," while others are easy, but this can only be determined by context.
No. The adjective hard describes work.Used as an adjective, the term hard-working can be hyphenated. e.g. hard-working man.