I thought this was a pretty interesting insight regarding character motivations. The article is talking about Superheroes, but this also applies to character-oriented fiction.
The io9 article makes the point that the motivation comes from the origin story saying: "as [Gail] Simone [writer of Birds of Prey and Secret Six] puts it, the point of the origin story isn't really to explain how the hero got his/her powers, it's to explain 'what they most desire, what they most fear. The best origins, like Spider-man's, Batman's, and the like, encapsulate the character's reason to exist. The worst merely explain that a drum of radioactive waste fell on their head and now they can fly.'" (source)
I also liked what a reader of the article said in the comments section:
The 'super' of 'superhero' is much less important than the 'hero' component. (source)