John's story is one that suggests heroism as an underlying thematic feature. For instance, he is the source of conflict in his mother's marriage, leading to fights that serve as his heroic "inciting incidence." He leaves his family's home and departs into the world to be tested and refined through experience, but he cannot succeed alone. He depends on the help of new communities that help him to understand himself in a different context than his own family dynamic.
Lucy Potts is an important part of his journey because his heroic decision to kill the snake that bothers her (like a knight slaying a dragon to win a princess, one might notice) comes at a time when his self-esteem is in need of assurances, and Lucy's hesitance to accept his affections signals that dilemma. Then, when he wins her affection, that helps him to believe that he can be someone impressive. His decision to marry her and move with her to a new place is a signal that he has completed the goal of his quest—to depart one family and establish a new one.
Unfortunately, things aren't perfect in their new family. Yes, he finally earned the respect he was always entitled to, but convincing Lucy to love him is a kind of addiction that John soon succumbs to. Over time, his love from Lucy is easily taken for granted, and he misses the thrill of convincing a woman to love him. So, he starts seducing women, using his self-righteous role as town pastor as an avenue to become emotionally intimate with women. John's life is tragic, and his hubris is that he knows he deserves love, but he can't figure out how to sustain a source of love for himself in his own self. He is desperate for approval that he cannot decide to award himself.
