Let's say you have a system for taking standardized tests. They're fairly common; many students and instructors have ideas about what kinds of multiple-choice answers to eliminate, for example. However, you take a new test and your tried-and-true methods fail. Do you tweak your methods for test-taking? In a situation like that, how do you determine what to change?
IME, the above kind scenario is relatively easy to learn from and adjust to. The real challenge comes when your ways of dealing with people fail.