I am reading a fascinating book on motivation (always helpful in "getting things done") entitled "Unleash the Warrior Within" by Richard Machowicz, a former navy seal.
Basically, he uses the paradigm of target, weapons, and movement, i.e. the target dictates the weapon which dictates the movement necessary to hit the target. Although he comes from a military background, his advice seems helpful in business too.
He discusses positive and negative "self-talk", motivation, goals, working through fear, etc. A fascinating read and a very good book on motivation and a fine supplement to GTD.