Want as Desire and Need

You can't always get what you want
But if you try sometimes, well, you might find
You get what you need
— Rolling Stone

In his book The Anatomy of Story, John Truby says that a character has both desire and need.

Desire drives the story. It is:

what your hero wants in the story, his particular goal.

But your character also has an even deeper want: their need. Need is:

what the hero must fulfill within himself in order to have a better life. It usually involves overcoming his weaknesses and changing, or growing, in some way.

This need develops from your character’s weakness, which occurs because:

something is missing within him that is so profound, it is ruining his life.

For Truby, desire and need are “intimately connected.” The needs of a character will drive their desires.

A character may need to protect his family, so he has the desire to threaten the villain when they come too close.