Sisyphean
Etymology
From Sisyphus, the cunning king of Greek myth who cheated death and was condemned by the gods to roll a huge boulder up a hill in the underworld, only to watch it roll back down each time he neared the top — for eternity. Albert Camus later made him a symbol of absurd human perseverance. The adjective names any labor with that same hopeless, repeating shape.
adjective · /sis-uh-FEE-un/
Endlessly laborious and futile, like a task that must be repeated forever without ever being completed.
What it names
The exhaustion of effort that resets to zero the moment you finish — reach for it when work is not just hard but doomed to undo itself, again and again.
Example
Keeping the shared inbox at zero felt Sisyphean: for every message I cleared, three more appeared.
Related idea
Futile simply means pointless; Sisyphean adds the grinding element of repetition — the same effort, endlessly renewed and endlessly erased.