The goal of this pilot study is to evaluate the feasibility and acceptability of collecting ecological momentary assessment data regarding feeling states during physical activity among a cohort of breast cancer survivors, using a novel smartwatch app created by the study team called "PHITbit."

Inclusion Criteria:

• Within 5 years of completing primary cancer treatment (surgery, chemotherapy, and radiation) for Stage 0-III breast cancer.
• Own an Android or iPhone smartphone and willing to use the smartphone to complete app-based surveys during the assessment period.
• Willing to wear the ActiGraph monitor during the assessment period.
• Willing to wear the study issued Fitbit Versa 3 smartwatch during the assessment period.
• Access to internet to complete REDCap survey assessments.

Exclusion Criteria:

• Non-English speaking/not able to read English.
• Evidence of major contraindications for exercise per the 2020 Physical Activity Readiness-Questionnaire (PAR-Q)+.
• Currently pregnant.
• History of severe mental illness or currently taking mood stabilizing medications (antipsychotics, anticonvulsants, or lithium).
• Evidence of moderate-severe depressive symptoms (indicated by a score ≥ 10 on Patient Health Questionnaire-8). -Evidence of moderate-severe cognitive impairment (indicated by a score < 3 on a 6- item cognitive screener).
• Evidence of clinically significant substance use as indicated by a score of ≥ 2 on the CAGE-AID screener.

Patients under the care of a Dartmouth Cancer Center oncology provider.