Social Network Service (SNS) users are more incidentally exposed to heterogeneous expressions than those engage in off-line discussion networks. The literature has mainly focused on how participation in social media affects users' subjective well-being, while overlooking how the heterogeneous expression on social media affects the users' subjective well-being and consequent behaviors on SNS. Underlining the undesirable consequences of the users' exposure to opposing views, this study developed a conceptual cognitive framework on the theory of cognitive dissonance, the extreme discomfort of simultaneously holding two conflict thoughts, and showed the existence of mental discomfort of the user in the face of heterogeneous opinions. We also discussed the kind of strategic behaviors the users may take to resolve the uncomfortable psychological state. To test, we first utilized projective technique to measure the uncomfortable psychological states of the respondents, and applied a covariance based structural equation modeling (CB-SEM) methodology with 425 questionnaire responses collected from Prolific Academic (Prolific.ac). We found that the more the users use social media, the more often they are exposed to opposite opinions and the more uncomfortable they feel. In order to resolve these uncomfortable feelings, it appears that these users tend to take selective exposure more than affective behavior. Robustness tests were conducted to check the controlling effects of personality traits and demographic variables on the main variables.