Recently, I've seen a TED TALK where Andrew Stanton(Pixar) was talking about stories, and the art of storytelling. He pointed out strongly that each well drawn Character, and usually MC's needed a "Spine", something that drove them, their unconscious goal, a motive that they were after. Michael Corleone from The Godfather- to please his father. Woody- to do what's best for his child, Marlin- to keep his child from harm, to quote a few.
So just out of curiosity, does your main character's have a "spine" and if so what is it?
Interseting question
I think that the spine of my charachter is the indecision, the disability to choose the path he should follow in his life.
And all what results from this state constitute the main elements of my story.
My protagonist is a chivalric knight. He has sworn to return to his beloved homeland and cleanse it of his enemies. But to do so he has to rise through the ranks and win the favour of the King. He takes huge risks to achieve his ambition and is twice badly wounded. This makes him more determined to succeed.