What was the most influential concept/theory/idea you have learned during the course?

In this post, I would like you to indicate one most significant takeaway - whether this is a model, concept, idea, or approach - anything that you find inspirational, thought-provoking, or of particular practical value (LEADERSHIP and CHANGE).

Please, explain why you think this to be of importance, and how you are going to apply this knowledge in your leadership practice (or have already applied it before). Illustrate with examples.