Creativity works in waves. It's not that you can sit down every day from 8 a.m. to 6 p.m. and expect to do your best work. Rather, it's an ebb and flow. You still need to show up every day, but it's not about forcing it. It's about being present and letting it come to you.
The same is true for knowledge work. There's a harsh local maximum to what you can achieve by forcing work. You create the illusion of working toward the goal you've set, but the goal itself is constrained by its own nature. Working in waves follows the model of sprint and recovery—ebb and flow. It's about contemplating what to work on and then pursuing it with determination. But you need space after periods of dedicated work to contemplate, reflect, and think deeply.