Best programming advice you've ever been given

[Mike]

What is the one piece of programming advice you were given that has really made an impact on you? The one you will never forget. Mine came from my dad. This was back in the days before Visual Languages (e.g. Visual Basic). You had to code your interface and your program code then. But the sentiment has always stuck with me. He said, "Write your interface like you're dealing with the smartest people on Earth. Write your code like you're dealing with the dumbest."