Personality plays a huge role in successful decision making. First people are filled with doubt and hesitation. "He who hesitates is lost." Most people miss opportunity because they are unable to strike while the iron is hot, due to lack of confidence. Point being, genetics determine personality and you can check out the very unethical separated twin studies to have an idea to what extent. Specifically, intelligence does not have nearly as much to do with successful decision making as confidence does.