Nearly every U.S. president has found himself in the position of figuring out life after the presidency.
Former presidents have demonstrated there are multiple ways to adapt to life outside of Washington and the Oval Office, and the word "retirement" does not quite apply.
George W. Bush's quiet service
When former president George W. Bush left the White House in 2009, he largely left the spotlight.
But last year he worked alongside volunteers in Zambia to renovate a clinic that specializes in treating cervical cancer. Like other former presidents, Bush uses his fame to draw attention to issues, but says he prefers not to call attention to his own work.
"I hope you don't see much of it, because I don't want to be in the news," said Bush as he took a break from painting. "In other words, I believe that quiet service is the best kind of service."
Former presidents have the ability to harness the public's attention and goodwill. President Barack Obama tapped Bush and former president Bill Clinton to lead a fundraising effort in 2010 after the earthquake in Haiti.
"On behalf of the American people, I want to thank both of you for returning to service and leading this urgent mission," Obama said at the time, standing alongside the two former presidents outside the White House.
Men who once led the nation can find themselves without a clearly defined role when they leave office.
"If you've been president, you know how limited the role of a former president in any sort of institutional way should be," says presidential historian Richard Norton Smith. "There are presidents who call upon former presidents in all kinds of ways to be of assistance."
Clinton and former president George H.W. Bush visited Indonesia after the devastating tsunami in 2004, and they raised funds and awareness after Hurricane Katrina ravaged parts of the southern U.S. in 2005.
Bill Clinton's global challenges
Clinton has remained in the public eye since his presidency, working as a U.N. special envoy to Haiti, pressing North Korea to release American prisoners, and campaigning for his wife, Hillary Clinton, when she ran for president in 2008.
Clinton also founded the Clinton Global Initiative, which he says "was designed to tackle big global challenges in bite-sized pieces."
George H.W. Bush's personal causes
Like his son, former president George H.W. Bush has little interest in pursuing high-profile work, preferring personal causes instead, according to Mark Updegrove, director of the Lyndon Baines Johnson Presidential Library.
"It's a relatively passive post-presidency," says Updegrove. "Of course, the most significant chapter in his post-presidency was when he became the father of the president of the United States."
Historians say post-presidential life has evolved. Prior to 1958, ex-presidents weren't granted pensions - let alone office space, staff and other benefits that give them a degree of freedom to pursue various interests.
Modern technology also links presidents to the public.
"As the presidency has become part of the 24/7 news cycle, presidents come into our lives. They come into our homes more than anyone except members of our immediate family," says Smith. "Whatever our partisan loyalties may be, we establish relations with them and their wives and their families."
Ronald Reagan chose a public life
Such is the case with one-time movie star and former president Ronald Reagan, who left office in 1989. He published a letter in 1994 revealing he'd been diagnosed with Alzheimer's disease.
His wife, Nancy, said they considered it an opportunity to raise awareness.
At the time, Nancy Reagan noted they'd been "public people our entire married life." She added, "If we can make a difference through our involvement, then we simply have to get out and do it."
Post-presidencies reflective of their character
Former presidents can devote themselves to chosen causes in a way they couldn't while in office, according Updegrove, the author of various books on the presidency.
"I think in many ways that the post-presidential activities of our former presidents are more reflective of their character than their years in office, which tend to be more insular in nature," says Updegrove. "When you're president, you can't always set the agenda. You have to react to events around you, nationally and internationally, so you might come in with ideas of what you want to do, but your presidency turns into something far different."
Post-presidency for an unelected president
Former president Gerald Ford did not even campaign before his presidency. He was serving in Congress when disgraced president Richard Nixon nominated him, as the Watergate scandal enveloped the sitting president's administration.
Ford, who served as president from 1974 to 1977, is known to have valued the advice of his wife, Betty, respected for her candor and outspokenness.
In 1978, Betty Ford sought treatment for prescription drug and alcohol use. Four years later, she co-founded the Betty Ford Center, which treats patients with substance abuse issues.
"He was so proud of her. He was very, very much an active foot soldier, for example, in the Betty Ford Center," historian Smith says. "Every year they had an alumni event, and he could be found cooking hot dogs."
Carter's 'adventurous and unpredictable' years
Former president Jimmy Carter's work often focuses on health, human rights, and democracy promotion, including election monitoring. He says his life's interests did not change when he left office back in 1981.
"I would say, and I think my wife would agree, that the time we spent since the White House has been the most exciting and productive and adventurous and unpredictable and gratifying time," said Carter.
He cited his work with his foundation, the Carter Center, his teaching position at Emory University in Atlanta, Georgia, and his large family.
Carter and his wife, Rosalynn, are well known for their work as volunteers with Habitat for Humanity, a group which helps low-income working people to build and buy their own homes.
"All of those things put together and still living in the same little town of 600 people, where my wife and I were born and where we own land since 1833, all those things combined together have given me a very wonderful life since the White House," Carter says.