Perhaps in bouts this very tedium is reassuring but it is not really applicable to compare all instances of writing to long-distance running.
To me, short stories are like choreographed dance or gymnastics routines: 90% preparation and 10% execution. Poetry is akin to fire-eating- pulling the flames out in dazzling displays and playwriting is coaching a team of players into a cohesive whole.
I am three-quarters of a way through two novels now. It has been like fencing for a long series of bouts- just me on the piste and up against opponents I cannot make out. In the beginning I had to sit on the sides a lot and just train until I could step back in again. Now I am a pro but I am still learning.