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.

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.