The effectiveness of positive psychology interventions relies heavily on participants' buy-in and personality traits. The Best Possible Self (BPS) intervention asks participants to envision their ideal future, supposing that everything goes smoothly. The BPS shows salient effects in improving subjective well-being in laboratory settings. In this study, the BPS was integrated into a real-world graduate-level online course as a series of assignments. A convergent mixed method was used to explore the participants' attitudes towards the BPS and the relationship between their personality and subjective well-being. A total of 86 students registered in both the summer and spring semesters of 2020 participated in this study. Pearson correlation results show significant correlations among attitudes, subjective well-being and gains and openness to experience. The results from open-ended questions confirmed participants' positive attitudes towards the BPS. This study contributes to the practical application of BPS in real-world, online, higher education courses.