There are a lot of reasons why, but the one that is relevant to this thread is not grasping the following: not realizing that people who stand out in life are so adept at picking themselves up from failure, do it so rapidly and seamlessly, have had so much practice at doing it that you don't even recognize they do it.
Practice doing that. No matter how insignificant the task is. My threshold for failure now is not doing that, and not pushing myself in life tasks where it really matters to me personally. (Important to distinguish.) And I'm already seeing a difference.