“She said, you work very hard on a problem for a long time, and then you get this rush, this wonderful satisfaction when you’ve solved it.”
Knuth fills piles of half-used scratch paper, writes everything up, and calls hoarding a solution selfish. The rush of solving a problem lasts about an hour, then the next one takes over. No productivity app appears anywhere in the method. Paper, stubbornness and decades of time did all the work.