Hansei (反省, "self-reflection") is a central idea in Japanese culture, meaning to acknowledge one's own mistake and to pledge improvement.
This is similar to the German proverb Selbsterkenntnis ist der erste Schritt zur Besserung, where the closest translation to English would be "Insight into oneself is the first step to improvement".
In the hansei process, the emphasis is on what went wrong and on creating clear plans for ensuring that it does not reoccur; this is done constantly and consistently.
At Toyota, even if one completes a project successfully, there is still a hansei-kai (reflection meeting) to review what went wrong.
In Japanese companies it is common practice for a manager to expect hansei from his subordinates in case of mistakes.