What does Ecclesiastes 4:8 mean?

There was a man all alone, with no family or children, yet he never stopped working and never seemed satisfied with what he had. He kept asking, 'Who am I working for? Why am I denying myself enjoyment?' This, too, is pointless and a miserable way to live. Ecclesiastes 4:8 - Modern Text Bible

(He describes someone who works endlessly for no one but himself, never enjoying life, and calls this a sad and empty existence.)