12074 Background: Advancements in cancer treatments have contributed to people living longer with Stage IV cancer. People living with advanced cancer face significant and unique psychological challenges related to dynamic treatment schedules, fluctuating physical symptoms, and uncertainty regarding prognosis. Understanding what constitutes a “good day” may help patients, their family members, and clinicians to recognize and prioritize factors that improve quality of life. The goal of this project was to understand activities and behaviors that characterize a “good day” among people living with advanced cancer. Methods: We enrolled 20 patients with advanced cancer (M 63 years old, range 41-75; 65% female; 65% white and 35% black; mean 1.5 years since Stage IV diagnosis [range 9 days to 7.5 years]). Participants completed semi-structured interviews and two weeks of nightly diaries, using a 1-5 rating scale (1 = very bad, 5 = very good) to rate their daily quality of life and document various activities and experiences. We conducted t-tests to determine differences in “goodness” on days with and without different experiences along with a Pearson correlation between each patients’ mean goodness rating and Patient-Reported Outcomes Measurement Information System (PROMIS) scores. Results: Interviews revealed themes of "good days," including emphasizing control, normalcy, positive impact, and presence. Loss of control, uncertainty, disruptive symptoms, negative healthcare experiences, and unmet goals were more common on “bad days.” Nightly diaries revealed significant correlations between active engagement in social, hobby, club, religious, cooking, reading, and meditation activities and reporting a good day (all p values < .05). Mean diary goodness ratings correlated positively with Ability to Participate in Social Roles/Activities (r(19) = .54, p = .016) and inversely with Anxiety (r(19) =-.63, p = .004) and Depression (r(19) = -.53, p = .020) and was marginally inversely correlated with Fatigue (r(19) = -.44, p = .059) and Pain Interference (r(19) = -.46, p = .050). No significant correlations were observed with Physical Function (r(19) = .15, p = .544), Cognitive Function (r(19) = .36, p = .134), and Sleep Disturbance (r(19) = -.26, p = .286). Conclusions: Preliminary findings suggest that days on which individuals with advanced cancer are able to engage in activities that give them a sense of normalcy, control, self-identity, and connection to others are better than days without these activities. This is further supported by the positive correlation between goodness ratings and the ability to participate in social roles and activities. Understanding the individual’s values, perceived social roles, and priorities may help care teams support people with advanced cancer to optimize their quality of life and functioning and navigate treatment decisions.