Choosing the right behavior can oftentimes be an act of balance between one’s own preferences or tendencies and momentary situational affordances. How do people navigate these potentially different requirements? One way would be to choose the behavior that makes one feel good. Specifically, we argue that fit between personality traits and personality states and fit between personality states and situation characteristics should be associated with positive affect. Thereby, fit may provide feedback to within-person processes of personality state expression. In two experience sampling studies (Study 1: N = 194, 4,244 observations; Study 2: N = 254, 7,667 observations), we employed moderated multilevel polynomial regressions and response surface analysis to examine whether trait–state fit and state–situation fit were associated with state affect. We found a consistent pattern of interactions between personality traits, personality states, and situation characteristics predicting state affect, but did not find evidence for the hypothesized trait–state fit patterns or state–situation fit patterns. These findings have two main implications. First, the results suggest that fit patterns are not involved in associations between personality traits, personality states, situation characteristics, and state affect. However, because theories proposing fit are often imprecise regarding the operationalization of fit, it is difficult to draw concrete conclusions about these theories. Second, the large number of interactions between personality traits, personality states, and situation characteristics suggests that these three constructs should be studied together. The specific role of these interactions for personality processes needs to be further determined in future research.