According to the internal/external frame of reference (I/E) model (H. W. Marsh, 1986), students not only compare their own abilities in a domain with those of other students (social comparison), they also compare their own achievements in different domains (internal comparison). The main purpose of this study was to investigate internal comparison processes in everyday life using an introspective methodology. Over 2 weeks, 67 university students (Study 1) and 65 high school students (Study 2) using a diary instrument recorded more upward than downward internal comparisons, most of them triggered by academic achievement situations. In both studies, multilevel analyses showed links between the direction of comparison and affective state: (a) upward internal comparisons were associated with negative mood states; (b) downward internal comparisons were associated with positive mood states; (c) upward internal comparisons increased positive and decreased negative mood states; (d) downward internal comparisons decreased positive and increased negative mood states.