ATLANTA — When Jimmy Carter left office in 1980, the return home to Plains, Ga., was not easy. His once-flourishing farming business was more than $1 million in debt, and he faced the prospect of selling the land his family had been on for 150 years.Then a friend pointed out that Carter, at the tender age of 56, could expect to live at least until 80 years old.“I had one disturbing reaction,” Carter wrote in his 1998 book, “The Virtues of Aging.” “What was I going to do with the next 25 years?”Let’s just say a lot — from establishing the Carter Center and being awarded the Nobel Prize to building Habitat for Humanity homes and writing more than two dozen books.March 21, 2019, marks yet another milestone.