In this experimental intervention, 121 adults participated in a randomized control trial testing whether daily reflection on social and nonsocial aspects of wellbeing is beneficial for mental and physical health. Every day for seven weeks, participants randomly assigned to the social wellbeing condition were asked to reflect on daily social interactions and rate how close and in-tune they felt during the interactions. Participants randomly assigned to the nonsocial wellbeing condition were asked to reflect on daily enjoyable events and rate how meaningful and rewarding the events had been. Participants randomly assigned to the control condition were asked to reflect on daily tasks and rate how useful and important the tasks had been. Results indicated that both wellbeing conditions prompted people to engage in more discrete daily social interactions, which in turn reduced their feelings of loneliness relative to the control condition. In addition, the two wellbeing conditions prompted decreases in illness symptoms relative to the control condition, but only among middle-aged and older adults. These findings may shed light on how people can fine-tune their daily thoughts and behaviors in order to become more socially engaged in their daily lives and ultimately promote lasting changes to their health and wellbeing.