The first lesson: The life is a constant struggle, so be prepared for the next challenge.
The stage of success is temporary and the forerunner of a new challenge. At the end of the Star Wars VI, Luke Skywalker kills the emperor and a period of peace and tranquility begins in the galaxy.
In time Luke vanishes and in his absence, the evil First Order rises from the ashes of the Empire. First Order is trying to control the galaxy as the Emperor once did. The peace again leaves its space to terror and war. Read more Lessons from Star Wars VII: The Power Awakens