Most information systems (IS) usage studies have investigated value assessment and behavior of social media use from a rational choice perspective. The changing paradigmatic landscape, however, suggests that the non-rational use of social media has ramifications beyond the current knowledge domain. Implementing a grounded theory approach, this study theorizes and juxtaposes the effect of both rational and non-rational factors on value assessment and behavior of habitual social media use. Identifying attributes, situations, and processes of habitual social media use, the study suggests that, when people develop usage habit with social media, they weigh the importance of social media attributes both rationally and non-rationally. The study develops a theoretical framework suggesting that habitual users exhibit both rational and non-rational tendencies in value assessment and behavioral choices of social media use. By taking both rational and non-rational cognition and their dynamics into account, this study extends the literature scope of IS use theory, and provides practical implications for social media organizations and managers to improve service effectiveness, long-term prosperity, and marketing extension.