This study contributes to understanding why some people but not others decide to start an own business. As part of a person’s personality, we focus on generalized beliefs about the efficacy respectively supportiveness of the self and of external factors. Using moderation and mediation arguments in a choice model, we suggest that a personality that makes a potential entrepreneur perceiving higher chances of entrepreneurial success may not make this person more likely to become an entrepreneur, because the attractiveness of a non-entrepreneurial occupation could be raised even more. We hypothesize that besides a positive association between entrepreneurship and general self-efficacy, there is a negative association between entrepreneurship and generalized beliefs about the efficacy of external factors, such as luck and other people’s support.