Wes referred in our Spinoza discussion to Antonio Damasio, a figure in neuroscience influenced by Spinoza. Here he describes the emotions' role in decision-making:
Watch on youtube: http://youtu.be/1wup_K2WN0I
Spinoza agrees that decision-making is based on emotion. Even a "rational" decision, i.e. one made in a calm manner by considering the alternatives, requires an emotional component to actually choose a path and move forward.