Previous work suggests that two key predictors of success across a variety of domains are self-control and emotional well-being (EWB). In the current project, we explore the relative contributions of these two factors to success in two domains: academic and professional achievement, and interpersonal relationships. Across five studies (N = 1130, 51.06% female), we find that although both are important to success, self-control is more predictive of success in achievement-related domains, while EWB is more predictive of success in relationship-related domains. This finding holds for college students (Studies 1 and 5), middle-school students (Study 2), East Asian adults (Study 3), and North American adults (Study 4), suggesting that it is cross-cultural and robust across age and measurement.