I saw this article today and thought it was a good example of why it can be good to take breaks from working every couple hours. When you stare at the same thing for a long time you stop seeing it.
https://www.thesun.co.uk/news/6015380/optical-illusion-troxler-fading-colours/
Wow. I'm going to use this to highlight the value of code reviews and external QA at work. It is so easy to get hung up looking at one detail that we tune out everything else.