The fourth arcanum is about work that was not done although the person was answerable for it. Not about tiredness and not about rest, but about what was dropped halfway and left others to suffer for it: the unfinished building, the thing nobody watched over, the matter put off until it turned into disaster.
In the lineage this turns into affairs that are never carried through. Things are started willingly and finished rarely; work is devalued — one's own and other people's; a feeling appears that effort leads nowhere. The habit of waiting for someone else to finish the job often goes with it.
The working-off is to carry through to the end what has already been started, even once it has stopped being interesting. And to take responsibility for the result rather than for the effort: done or not done, with no explanations in between. One finished undertaking weighs more here than ten begun.