When a once great footballer loses his lustre, his manager no longer picks him; when a legendary golfer fails to keep pace with the kids, he joins the seniors tour.
But when a celebrated fighter can no longer defend himself, people line up to tell him he can still be the champ and arenas and television networks vie to stage his bouts.
Such is the lot of Evander Holyfield, four-time heavyweight champion of the world turned punch bag to the mediocre.
Holyfield, 42, has earned an estimated $150m (£80m) in the ring during a 20-year career, which makes his continued pursuit of the undisputed world heavyweight crown puzzling.
That Holyfield has already won the undisputed championship once, way back in 1990, makes his quixotic quest even more baffling.
On Saturday, the fighter formerly known as the "Real Deal" was humiliated by Larry Donald at New York's Madison Square Garden on the undercard of an underwhelming world title double-bill.
Headline act no longer and with two wins from his last nine fights, Holyfield still thinks he has the tools to accomplish his goal and still believes it is God's will he should do so.
HOLYFIELD'S LAST NINE FIGHTS
Nov '04 Larry Donald (L)
Oct '03 James Toney (L)
Dec '02 Chris Byrd (L)
Jun '02 Hasim Rahman (W)
Dec '01 John Ruíz (D)
Mar '03 John Ruíz (L)
Aug '00 John Ruíz (W)
Nov '99 Lennox Lewis (L)
Mar '99 Lennox Lewis (D)
"You can't choose your beginning and you can't choose how you want to end and my chosen goal is to retire as undisputed heavyweight champion of the world," Holyfield told BBC Sport before his latest debacle.
"You can only lose if you quit - so as long as I don't quit I'll reach my goal."
Which prompts the question, where do you draw the line?
When you are a quivering shell like Muhammad Ali?
Or when you are paralysed down one side like Greg Page, the former WBA champion who, like Holyfield, didn't know when to walk away.
Holyfield is unable to escape what sports psychologist Paul Dent calls his "athletic identity".
"Sportsmen are defined by the sport that they play," explains Dent of Brunel University.
"If Holyfield's not a boxer, what is he? Boxing's one of the most glamorous sports in the world - you're idolised, known throughout the world. To leave that behind is difficult.
"You are defined by that persona and when these people go back to relative obscurity the desire to return to that former glory is often too much."
Then there is the inner circle, the people who should have told Holyfield to quit when he was battered by James Toney last October.
Holyfield sacked his long-term trainer Don Turner for having the good sense to stop that fight and has since brought in a team that will do as he says.
"Yes men", as Lennox Lewis' former manager Frank Maloney calls them.
"Fighters are blinded by people around them, people who are making money out of them," says Maloney.
"There's always people whispering in their ear, people persuading them they are better than they are.
"And too many managers are keen to keep their fighters fighting even if they know they should retire."
Holyfield sees it differently.
"No-one should ever be able to make a decision for someone and if you are not going to believe in someone you shouldn't be with them.
"So I chose someone (trainer Ronnie Shields) who believes that I can and that's going to make the difference.
"My family believe daddy's a rock, they believe daddy can do it - and they've been taught by me that if you don't quit you'll get it eventually."
Someone should tell Evander's kids that if hit hard and often enough, even rocks can break.