In study phase 1, the investigators will prospectively examine the factors related to post-operative glycemic variability and its effect on outcomes in people with both DM and GI cancer after surgery. The study will also qualitatively understand the glycemic variability experiences and their associated symptoms and outcomes in people with both DM and GI cancer. In study phase 2, the investigators will develop and test the effects of the CGM-Assisted Reflection Education (CARE) program on adults with both DM and GI cancer post-surgery.