"Any fool can write code that a computer can understand.
Good programmers write code that humans can understand."

— Martin Fowler,
Refactoring: Improving the Design of Existing Code

Martin's should be a corollary of Brian Kernighan's quote which is

"Everyone knows that debugging is twice as hard as writing a program in the first place. So if you're as clever as you can be when you write it, how will you ever debug it?"

@asgs Never because if you're as clever as it can get while writing it, there will be no bug.

(I know, unrealistic but your comment wasn't realistic either)

@filthyranter clever != understandable. The point Brian made is, the cleverer the coder gets, the tougher the trap the machine will get you into.

Also, you meant that quote wasn't realistic. All my comment did was quote that quote

the reall hard thing is to create code that is efficient AND understandable. the most clean code ideas are often leading to less Performance on runtime. thats a tradeoff and there are Places where code readability is not that important as Performance. like in shaders, or heavy (really heavy) database Operations or Iterations.

The first thing every new programmer must be taught.