This constructivist (naturalistic) study explored the decision-making strategies of patients with multiple myeloma who were implementing a home-based exercise program intended to decrease cancer-related fatigue during therapy. A purposive nonprobability sample of 21 patients who were undergoing an aggressive tandem transplant protocol provided data through face-to-face and follow-up telephone interviews. Salient themes derived from the data through content analysis and constant comparison included intrinsic and extrinsic facilitators and barriers that influenced the participants' day-to-day decisions about exercise. Intrinsic factors that facilitated exercise adherence included a belief that exercise would be beneficial, a personal moral/ethical philosophy with regard to honoring a commitment and/or taking responsibility for one's health, and personal strategies such as keeping a routine and setting goals. Extrinsic facilitators included having a good support system and receiving prophylactic epoetin alfa. The experience of chemotherapy and related side effects were intrinsic barriers, while environmental factors such as weather, travel, and employment could be either facilitators or barriers. The delicate balance within the matrix of facilitators and barriers influenced participants' daily decisions about starting, interrupting, stopping, or resuming their workouts.