Overwork (n.) is a breach of contract: you pay me for one day's labour-power while using three days of it.
Overwork (n.) becomes boundless only where exchange-value rules; in antiquity it turned frightful only in mining gold and silver — forced labour until death.
Overwork (n.) pays the worker less the more he works, because he competes against his fellows and in the last analysis against himself as a member of the working class.
Overwork (n.) makes one worker do what it would be rational for two to do, and where that one can replace three it raises the rate of surplus-value even as the mass falls.
Overwork (n.) of the employed swells the reserve army, and the reserve's competition forces the employed into over-work — one part condemned to idleness by the toil of the other.