To add to your anecdote: Darwin wrote On the Origin of Species with a day that ran: Breakfast and a walk; 90 minutes of writing; spending time with his wife reading their letters and a novel; another 90 minutes of writing; and lunch.

After lunch was attending to his correspondence, reading with his wife, then dinner and games.

For all the talk of "crushing" and "changing the world" I doubt that anything almost anyone here works on or ever has worked on will have the same impact as Origin. The cult of productivity is unhinged, madness.