In order for the characters in your story to grow, Lagos Egri informs us, you must lead them into situations of increasing conflict.
Conflict emanates from contradiction. Contradiction results from the clash of two powerful wills, pitted against each other. Animosity, fear, jealousy, covetousness, hate, and overbearing ambition pitted against their opposites are some of the the ingredients that make for a powerful conflict.
Conflict will not thrive without heaping trouble and misery upon our characters. To rectify a wrong decision, they make another, then another, and a third to fix the second, and so on. This provides the causality that drives the story forward like a stack of falling dominos.
Some characters will eventually concede defeat. Others who are stubborn will never give up.
As a writer, your interest lies in characters who, by their physical and psychological make-up, are predestined to defy the odds and never give up. They are reckless. They try to achieve their goal, no matter what.
Such driven people, however, become desperate only after dire necessity forces them to a decision, and any delay in acting might cost them their lives, loves, wealth, health, or honour. Desperate necessity propels these characters toward their ultimate goal, which is clearly stated in the story’s premise.
The greater the conflict in the characters’ lives, therefore, the greater their growth. End-to-end growth, such as from jealousy to trust, or from hatred to love, and how it happens, makes for the most exciting and successful stories.
Conflict promotes growth by causing contradictory traits to collide and resolve themselves into an outcome, where one trait gains prominence over the other.