Did you forget to say that this question is about "The Bass, The River, and Sheila Mant"
Answer:
The narrator's automatic actions move the plot because they show that Sheila is no more important than her fishing habit. This can create conflicts that will move the story.
Step-by-step explanation:
Although the narrator had pledged to take Sheila Mant to the dance, he didn't think twice before starting fishing halfway. Even if the narrator does this automatically, he shows how the habit of fishing this intrinsic in him, so much that it puts Sheila in second place in his priorities, since the fishing can make him late, or even that the boat tip over and he can't take you to the ball.
This moves the plot because it can be the source of several internal and external conflicts.