Adoption, acceptance and, more recently, continued use of information technology (IT) in workplace contexts have been researched extensively over the last three decades. As acceptance and use of IT underlie its ability to fulfill expected business benefits, it is unsurprising that researchers have sustained a great interest in the topic. While there is a wealth of cumulative knowledge on adoption and the factors affecting adoption, much less is known about specific patterns of use--ranging from extensive and frequent use to complete non-use--and the reasons behind these patterns. Existing research on both use and non-use of IT has, until very recently, emphasized the technical, cognitive and social aspects that may influence human-technology interactions. This has left other aspects--such as emotions and self-identity--of the relationships between social actors and IT relatively unexplored. Accordingly, the goal of this research is to bring people--including their "non- rational" sides--back into Information Systems research, without black-boxing either the IT artifact or the user. Three studies are conducted to achieve this goal; each study focuses on a different aspect of the emotions-identity-IT relationship. Overall, the research contributes to a better theoretical understanding of how social actor emotions and identity influence how and why certain IT systems and specific features of IT systems are used in the workplace, while others are not. The research also contributes to the development of a novel theoretical framework for the study of IT use and non-use from a "personalized" perspective. From the practical point of view, the research provides novel insights into how to deal with managerially undesirable patterns of use and non-use of IT at work. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]