Individuals with chronic conditions face challenges with maintaining lifelong adherence to self-management activities. Although reminders can help support the cognitive demands of managing daily and future health tasks, we understand little of how they fit into people's daily lives. Utilizing a maximum variation sampling method, we interviewed and compared the experiences of 20 older adults with diabetes and 19 mothers of children with asthma to understand reminder use for at-home chronic disease management. Based on our participants' experiences, we contend that many self-management failures should be viewed as systems failures, rather than individual failures and non-compliance. Furthermore, we identify key principles from reliability engineering that both explain current behavior and suggest strategies to improve patient reminder systems.