“A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.”

Simplified Meaning:

When people try to create something that they think no one can mess up, they often forget that someone might still find a way to do just that. Imagine you design a really simple phone that only has one button to make it easy for anyone to use. However, someone might still press that button too many times or at the wrong moment, breaking the phone. This happens because those making the design don't always account for all the ways people can creatively or unexpectedly make mistakes. For example, when car manufacturers create the layout of a car, they try to make everything straightforward, like where the gas pedal and brake pedal are. Despite this, there are still accidents where someone confuses the pedals. To apply this wisdom to your life, always consider that no matter how simple you make something, there will always be someone who can find a way to get it wrong. Therefore, it's smart to think ahead and plan for those unexpected ways errors can happen, making your designs or plans even more robust.