- Heavyweight boxing champion Evander Holyfield says he hasn't retired
- Basketball legend Kareem Abdul-Jabbar lives with leukemia in his retirement
- Martina Navratilova serves as AARP Fitness Ambassador
- Retired NBA player Kevin Willis can still bench press 315 pounds
Retirement terrifies sports stars. The end of a glittering career can feel like falling off a cliff to an athlete who thrives on fame and fortune. And the longer the career, the harder the end game seems to be.
For living legends, it's especially tough to know how to quit. World heavyweight champion Evander Holyfield turned 50 this year -- but he still wants to box professionally.
"I'm not retired," he says. "If I can get a championship fight, I will."
He won't fight just anyone, though -- only top boxers. Because he holds five heavyweight titles, he tells CNN that young boxers could want to challenge him just because they have something to prove.
Holyfield can still draw a crowd, nearly 30 years after his professional debut. During a recent visit to CNN Center in Atlanta, fans swarmed him, taking pictures and shaking his hand.
"I keep myself right at the (professional) level, in case somebody feels froggy and says, 'I think I'm going to whup the old man,'" he says. "And they'd be shocked."
He says he trains every day, so that he always feels ready to fight at the top level. But Holyfield also faces a fight outside the ring: He lost his Atlanta-area mansion to foreclosure in 2012.
So he understands the perils of quickly rising from modest means to riches -- then back again. He is trying to get his financial house in order. He recently took a sales role with Primerica, a financial services company. Holyfield sees it as an opportunity to teach others how to manage money.
"When I was 21 years old, I was a millionaire," he says. "You're talking about a guy making $8,000 a year, working 40 hours a week, made the Olympic team, went to the Olympics, two weeks later -- a millionaire."
When Holyfield signed his first million-dollar contract three decades ago, he had been working three jobs that together earned him less than $10,000.
"It was just all of a sudden," he says. "I came into boxing, I made big money."
But getting used to big swings in the bank account isn't the only challenge celebrity athletes such as Holyfield face. They also have to learn how to live without the constant cheer of the crowds once they're out of the spotlight.
Kareem Abdul-Jabbar, 65, was one of the world's most famous basketball players. He remains the record all-time scorer in the National Basketball Association. He still has to duck to get his 7-foot, 2-inch frame through most doorways.
But when he retired as a player in 1989, after 20 years of professional play, he was at a loss.
He told CNN: "The first training camp that I missed, I was like, 'Jeez, what am I going to do now?'" He quotes another sports legend -- Jackie Robinson -- to describe how he felt when he retired.
"He said that athletes die twice," Abdul-Jabbar said. "You know, when that first career is gone, that's a death."
That adjustment was harder for Abdul-Jabbar to process than his cancer diagnosis in 2008. He has chronic myeloid leukemia, a blood cancer that he manages with drug therapy.
"I think that (retirement) was the more difficult adjustment because you don't know what to do," he said. "I'd had this incredible career." But when he started to cultivate his talents off the court, he discovered a new calling. Now, he says, he wants to be known for his writing -- not just his basketball prowess.