After 20 years working as a designer and ten years as a creative director I have learned the importance of testing every step of a design process and it never stops to surprise me how often designs that I personally find really strong, about half of the times when performing usability- and perception tests, reveals serious problems. What I have come to learn from this is the importance of testing every major iteration of a design on an unbiased audience and never let my subjective opinion solely drive conclusions about a design.