As a graduate student at Rice University, I worked with an unconventional professor. He was not preaching math. He was teaching truth. He was dedicated to the years-long process of nurturing mathematicians: a refiner's fire for clarity in thought, a threshing floor for precision in communication. This professor served as a role model from whom I adopted many approaches to teaching.
"Take your work very seriously. Don't take yourself too seriously." We all experience disappointments, embarrassments, and frustrations. We often focus on how these setbacks affect our image (our selves) rather than our calling (our work). This cedes control over our response to those who determine our image. If we can have fun with ourselves -- unassailable self-worth and tongue-in-cheek self-deprecation are powerful partners -- and focus on the work we are called to do, our view of these setbacks and our response to them change dramatically.
When discussing "failure" and "success", we have certain goals in mind, explicitly or implicitly. When defining our goals, we have a tendency to look outward, rather than inward and upward. The more aware we can be of our goals, and the more worthy the source and motives of our goals, the more meaningful the notions of "failure" and "success" become.