I love this analogy from Melanie concerning the difference between a Main Character who changes their Resolve (think Marlin in Finding Nemo or Ben Cash (Viggo Mortensen) in Captain Fantastic ) and a Main Character who has their Resolve changed over time (think Jasmine (Cate Blanchett) in Blue Jasmine or Elliot in E.T.):
Sometimes, in geology, this force gradually raises or lowers land in two adjacent plates. Other times it builds up pressure until things snap all at once in an earthquake. So too in story psychology, people are sometimes slowly changed by the gradual application of pressure as the main character’s justifications gradually unwind through experience. Other times the pressure applied structure just builds up until the character snaps in Leap Of Faith – that single “moment of truth” at the climax in which a character must decide either to change his ways (or outlook) or stick by his guns believing his current approach is stronger than the pressure bought to bear against him, believing he just has to outlast the forces against him to ultimately triumph.
Follow the link to The Tectonic Plates of Story Structure for a great visual as well.