I try to reason about this a lot, and the trouble is everything I aspire to do happens across decades. Nothing that can be accomplished in a day or a week seems satisfying.
But this is not the point. The point is not to engage in meaningless or easy stuff only. The point is to recognize that you should not dedicate more than 8h per day because for many jobs (including software engineering) there are no deadlines or most are made by people that are not involved in the actual process so they are artificial limits imposed to make you fret.