The investigators developed a novel, telephone-based, 12-week positive psychology intervention and will assess its feasibility and short-term impact in adults with type 2 diabetes (T2D) and suboptimal health behavior adherence. Participants will receive a positive psychology (PP) manual, complete exercises (e.g., writing a gratitude letter, performing acts of kindness), and review these activities by phone with a study trainer over the 12-week study period.