My outlet install fiasco and the line level wake-up call
Honestly, I figured I could lay bricks straight without a line level for every course to save time. Tbh, I was overconfident. Last month, adding an outdoor outlet to a repaired brick wall, the rows seemed fine, but drilling for the conduit showed they were off. The outlet box wouldn't sit flush because the bricks weren't level. I had to redo a part, which was a big hassle. Since that job, I make sure to use a line level, even for simple jobs. Seeing the trouble it caused drove the point home.