Educating Joseph

Bereisheet contains many stories illustrating dynamic character transformations, demonstrating that people can overcome natural tendencies to improve. What does the story of Potiphar’s wife (from the following parsha) contribute to this end? Remarkable self-restraint is evident, but how is the story relevant to Yosef’s problems with his brothers, or to his management ability? Why is his success followed by further punishment and exile? There is another key aspect to the story.