I know a guy who was diagnosed with a rare incurable disease in his later 20s. When he asked how long he had, the doctor said it could vary, but there wasn't any way he'd live to see his daughter graduate high school. So he didn't worry about retirement, but he worked hard to leave something for his family. He agreed to participate in a global study of the disease, going in for regular blood draws and imaging.
Every other person in that study is dead. My friend is pushing 70, and no one knows why. He had no special treatment, there doesn't seem to be anything unusual in his genetics, but the disease hasn't killed him. He became an intense focus of research, and even got a tattoo of three dots on his hip so that they could line up the images exactly the same way over the years.
He said it was a real "oh shit" moment when he realized he was going to live to retirement.