This paper suggests a mechanism that describes individuals' positive self-image in subjective assessments of their relative abilities. The mechanism assumes individuals have heterogeneous production functions that determine ability as a function of multiple skills; make skill-enhancing investments with the goal of maximizing their ability; and make ability comparisons using their own production function. Within this framework, the paper provides conditions under which there is positive self-image. Positive self-image is increasing in the ease of the task, the number of different skills needed for the task, and the variability of production technologies in the population.