Inclusion Criteria  Must own an iPhone 6s or later (with iOS 14 or later or willing to update to iOS 14+) and be willing to complete surveys on it, per the protocol. Sleep aid usage will be allowed as long as the patient has been on a stable dose for at least 4 weeks prior to enrollment and agrees to continue the same dose during the study. A response of at least 4 on a 10 point scale (with 0 = not fatigued at all and 10 = extremely fatigued) to the question "How fatigued did you feel in the past week?" Breast cancer population: Diagnosed with stage 1-3 breast cancer in the last 10 years, without metastatic disease. Chemotherapy or radiation therapy, if indicated, must have been completed at least 3 months prior to enrollment. Concomitant anti-HER2 therapy and/or anti-endocrine therapy is permitted. Prostate cancer population: Undergoing androgen deprivation therapy (ADT) for at least three months and are anticipated to remain on ADT for the duration of the trial. Concomitant additional anti-androgen therapy (e.g., enzalutamide) is permitted. Autologous HSCT population: Participants must be from the University of Michigan Blood and Marrow Transplant Program.  Exclusion Criteria  The patient cannot be undergoing chemotherapy at the time of enrollment, but post transplant maintenance therapy that begins after enrollment is allowed. The patient must have no evidence of disease progression or recurrence. Specifically for the prostate cancer population, the patient must have no evidence of disease progression on their current ADT regimen at the time of enrollment. The patient must not be a night shift worker, where night shift is defined as working a significant number of hours (i.e. more than half) between the hours of 11PM and 6AM on a regular basis.