Hmm... I'm not too sure about your translation Thomas... luw is normally only translated as save when talking about saving
persons. Destroy or dissolve don't sound as good of course
Not sure what it means exactly though, maybe it's as Thomas said, you work now and save doing work later, but I'm not sure, I mean it depends on the context. It could be like that, but my guess is that this is a play on words, that is the word kopos has two meanings and both are used in this sentence.
so 'tiredness destroys work', as you can't toil or work when you're tired.