Mistakes in design and coding (and project estimating and requirements gathering) that you encounter continually through techniques like
PlanningGame,
TestFirstDesign,
PairProgramming and
RefactorMercilessly, and from which you continually learn about the customer's needs, about the project, about the system you are building, and about your coding practices and techniques. These are all techniques to
EmbraceChange.
By continually improving your work, increasing the likelihood that you are building the system that your customers actually want, on time and on budget,
LittleMistakes help you to avoid
BigPublicFailure.