The tricky part is that your brain fills in what it expects to see, so once you "know" red is positive you stop actually reading the wires. I've started doing a quick continuity beep test on every new run before powering anything up, takes ten seconds and it catches stuff my eyes miss. Also labeling spools with a piece of masking tape is stupidly cheap and has saved me way more than six bucks in lost time.

My mom kept a jug of white vinegar under the sink my whole childhood and I always rolled my eyes at it. Then last summer my AC started smelling like a wet dog and my neighbor Ray told me to run vinegar through the drain line. I did it twice, let it sit overnight, and the smell was gone by the next afternoon. I was honestly shocked because I figured it was just something old people did to feel useful. Now I keep a spray bottle of half water half vinegar in the garage and use it on everything. My grandma would be so smug if she were still around to see it.