The influence of the interplay between mobile phones’ and users’ awareness on User Experience (UX) of using mobile phone remains unclear. To fill that gap, a one-week logging study with 32 participants and a follow-up survey questionnaire were conducted. The usage of mobile phone applications are self-reported found to be both initiated by the self-awareness of the user and dependent on contextual factors. Active awareness of mobile phones deteriorated easily with decreasing computing resources due to increasing usage and thus triggered passive awareness in the user. We advance a conceptual model and discuss the implications for designing mobile context-aware systems and services. The outcome of this study lays the groundwork for comprehending the dynamics of UX for mobile context-aware systems and services.