Breathing Practice for Mental Health in Cancer and MS

Inclusion Criteria: * STUDY 1: Participants must be physically fit enough to perform light exercise. * STUDY 1: Should read and understand English well enough to consent, complete measures, and follow instructions. * STUDY 1: Must have access to a smartphone or tablet. * STUDY 2: Participants must be physically fit enough to perform light exercise. * STUDY 2: Cancer patients may have prostate cancer, neuroendocrine tumor, or brain cancer in any stage. * STUDY 2: The main focus is on pairs of cancer patients and their respective caregivers, but individual cancer patients or individual caregivers are also acceptable. * STUDY 2: Participants should read and understand English well enough to consent, complete measures, and follow instructions. * STUDY 2: They also must have access to a smartphone or tablet. * STUDY 3: Participants must be physically fit enough to perform light exercise. * STUDY 3: The patient should have multiple sclerosis. * STUDY 3: Participants should read and understand English well enough to consent, complete measures, and follow instructions. * STUDY 3: They also must have access to a smartphone or tablet. Exclusion Criteria: * STUDY 1: Participants incompatible with MRI machines due to factors such as pacemakers or metallic implants. * STUDY 1: Additionally, those with chronic medical conditions, including heart disease (coronary artery disease, congestive heart failure, hypertension, cardiac arrhythmia), chronic obstructive pulmonary disease (COPD), cystic fibrosis, cancer, diabetes, sleep apnea, aneurysms, and neurological conditions (epilepsy, Alzheimer's disease, Huntington' disease, essential tremor and Parkinson disease) are excluded. * STUDY 1: Participants with psychiatric conditions such as psychosis, suicidality, bipolar disorder, major depression, and substance use disorders are excluded. * STUDY 1: Participants serving as caregivers for any of the aforementioned conditions and for other illnesses such as cancer or neurological disorders, are also excluded. * STUDY 1: Further exclusions apply to those with severe vision, hearing impairments, have a body mass index (BMI) over 30, and those who are pregnant. * STUDY 1: Those planning to become pregnant during the study period will be excluded. * STUDY 2: Participants incompatible with MRI machines due to factors such as pacemakers or metallic implants are excluded, as are those with chronic lung disease (chronic obstructive pulmonary disease \[COPD\], cystic fibrosis), aneurysms, and those who are pregnant. * STUDY 2: Those planning to become pregnant during the study period will be excluded. * STUDY 3: Participants incompatible with MRI machines due to factors such as pacemakers or metallic implants are excluded, as are those with chronic lung disease (chronic obstructive pulmonary disease \[COPD\], cystic fibrosis), aneurysms, and those who are pregnant. * STUDY 3: Those planning to become pregnant during the study period will be excluded.