"We're getting paid to put paint on the wall."

I was like 17 or so and had a temp job as a housepainter for a couple weeks, and I was sinking time and energy into doing an excellent job and being really efficient with paint and ... kind of missing the forest for the trees. I was putting unnecessary care & excellence into a back wall and the wall was taking longer to prep than the whole-house job could afford. One of the old guys on site pulled me aside me and, in the eloquent terms above, pointed out that ... the real goal here is paint on the wall. We're doing a good job because we take pride in our work, but the outcome is significantly more important than the journey to everyone else. Doing a "good job" can't wind up as an obstacle to the job itself.

I was always a details person and perfectionist, and that one clear lesson about taking a step back from the details of a task to double-check what the actual goal is ... has always stuck with me.