Engineering mistakes can never be avoided. Don't be silly to believe that those mistakes stand for low level or void of excellence in PCB design capability. However, most of mistakes engineers tend to make derive from their excessive considerations in terms of system efficiency, signal integrity, low energy consumption and cost saving. Put another way, those mistakes result from "kindness". Therefore, awareness about the "kindness" and timely avoidance of those mistakes is greatly beneficial for the smooth implementation of your projects.