Honest self assessment is a big focus in our instructor training. We know that instructor candidates won't have us around after they leave our class, but they WILL have themselves. We work with them to build a set of solid skills, and an ability to accurately assess their own performance WITHOUT negative self-talk.
During a session yesterday, one instructor candidate demonstrated this beautifully by giving an example of a mistake he made while teaching the previous week. He told us that after class he was thinking about how the session went (amazing!), identified a particular interaction that he could've handled better (also amazing), and was able to name what he did wrong (super amazing), AND was willing to share it openly with others (unbelievable).
When instructors can make ongoing/honest self-assessment/improvement, the training industry will continue to improve. It feels amazing to be able to help individuals discover this ability in themselves :)