During the Covid-19 pandemic, social distance regulation calls for non-contact services, making self-service technologies gain much more attention. However, customers found they are pushed into more digital shadow work by employing Self-service technologies (SSTs). This research aims to examine how digital shadow work influences user emotions and behaviors during SSTs use. Based on the grounded theory method (GTM), this draft drives 128 codes and 7 categories to develop the theory of digital shadow work. Operations, consisting of pre-use, during use, and after use, along with the cognitions, including the perception of use-value and time efficiency, act as the trigger of digital shadow work. Achievement emotions, embodying happiness and satisfaction from technology use, result from the perception of high use-value and high time efficiency, while loss emotions, encompassing anger and disappointment from the user experience, generate from the perception of low use-value and low time efficiency, and finally, user responses from the digital shadow work - quitting, continuous and alternative behaviors are found as key factors. The interventing roles of a sense of control, system features, and compensation are also addressed. Examining users' psychological mechanisms academically contributes to developing the theory of digital shadow work whereas it advances the development of SSTs on a practical side.