on Writers Helping Writers:

The change arc. The process whereby, over the course of a story, the protagonist becomes aware of their weakness and evolves in whatever way is necessary for them to achieve their story goal.

Joseph Campbell called this kind of character The Hero with a Thousand Faces because, while each protagonist is different and they each have their own problems, their journey is the same. Their success and happiness are being blocked by a specific flaw that must be dealt with. And most of the time, when their story begins, they’re blissfully unaware that there’s even a problem.

So how do we turn our ignorant, stuck character into someone who recognizes their fault and actively works to overcome it?

Failure.

Yes, you read that right. Failure is the key to growth. When a character makes poor choices, acts impulsively, or lets fear get the better of them, things don’t end well. Failure generates more (and bigger) problems and conflict—which lead to more chances for them to either dig a deeper hole or climb toward the light.

Failures are learning opportunities. And just like parents have to sometimes let their kids fall down, authors must provide those same chances for our characters if we want them to grow.