The most common phrase is "nose to the grindstone," as in "He really has his nose to the grindstone this week."
working one's fingers to the bone
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
No, if something is "like" something else, it is a simile.
Life Is Sometimes Hard
It's not an idiom. "Fruits" means the end result of something, so "fruits of labor" would be what you earned from hard work.
more hard-working, most hard-working
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.
Pagsusunog ng kilay is a Filipino idiom that means working hard or burning the midnight oil in English. It refers to putting in a lot of effort and dedication to complete a task or achieve a goal.