One of the homilies I had rammed down my throat by high school coaches was "practice like you play." In the world of sports it just means to develop good habits and a high effort level in practice so that it carries over into the real games.
I fixed a bug yesterday at the last minute of our iteration that got through our automated FIT testing on the service layer because the automated tests were written at too low a level. It would have been more work upfront, but if I had made the FIT tests exercise the service layer the exact same way as the user interface, I could have saved time in the end. Lesson (re)learned.