If you avoid the killer diseases and keep the degenerative ones under control with sensible diet and exercise and whatever chemotherapy you need to stay in balance, you can live nearly forever.
The quote suggests that by actively preventing severe diseases and managing chronic conditions through a balanced lifestyle, individuals can significantly extend their lifespan. Emphasizing the importance of diet, exercise, and appropriate medical treatment, it conveys a sense of empowerment in health management.
In the context of the book "New Short Novels 2" by Wallace Stegner, this perspective reinforces the idea that longevity is attainable through proactive choices. It implies that a careful balance of self-care and medical intervention can lead to a fulfilling, extended life.