The last line of The Myth of Sisyphus is, “One must imagine Sisyphus happy.”
But for a while we were like Sisyphus pushing that rock up the mountain.
And a deal becomes possible only after all sides are exhausted—just like Sisyphus on the Hill.
King of Corinth, famed as "the craftiest of men," he was condemned in the afterlife to roll uphill a stone which perpetually rolls down again; Greek Sisyphos, a name of unknown origin. Liddell and Scott suggest a reduplication of syphos "the crafty" (with Aeolic -u- for -o-), but Klein calls this folk-etymology.
A king in classical mythology who offended Zeus and was punished in Hades by being forced to roll an enormous boulder to the top of a steep hill. Every time the boulder neared the top, it would roll back down, and Sisyphus would have to start over.
Note: A difficult and futile endeavor may be called a “labor of Sisyphus” or a “Sisyphean task.”