It may be disappointing for the rest of us to see Rebecca Adlington retire, but we aren't the ones who have to get up at 5.15am each day to train. At 23, she simply feels too old to win the biggest races now, she says. "I hate the word 'retired'," she told her press conference. "I'm not retired. Even when I'm 90 years old, I'll still be getting in the pool and going for a swim." But loving what you do and loving winning are two different things. The second one has driven Adlington to become Britain's greatest ever swimmer. You could understand if the distant gleam of bronze is not, perhaps, enough to swap for another four years of her youth.

And she has plans. Since the London Olympics, she has qualified as a level two swimming teacher. (Not a very tense exam, you would imagine.) She has also set herself another ambitious target by launching a programme called Becky Adlington's Swim Stars, which intends to get every child in Britain swimming at least 25 metres by the time they leave primary school.

Yet ultra-young retirement does not agree with everybody. Bjorn Borg suffered a double misfortune after he quit tennis at 26, first struggling in his business and personal life, then staging a disastrous comeback. Even so, Adlington can take some comfort from the more encouraging examples among her fellow 23-year-olds.

Nadia Comaneci, gymnast

It is perhaps easier to abandon the career you love when you know for certain that its highlight has already passed. At the 1976 Olympics in Montreal, when she was just 14, the Romanian gymnast Nadia Comaneci not only won three gold medals, a silver and a bronze, but also scored the first perfect 10 – on the uneven bars – in the history of the games. In Moscow in 1980, she won two more golds and two silvers, then ceased competing the following year, before retiring officially at a lavish ceremony in 1984.

This was not especially young for a female gymnast. They have perhaps sport's earliest and shortest careers. She may have been only 23, Comaneci likes to remind people, but she had been working hard since she was six. In 1989, she escaped Romania, climbing seven barbed-wire fences (very gracefully, you expect), to seek asylum in the United States, where she now lives. With her husband, Bart Conner, another gold medal winner, she runs a gymnastics academy, supply company and magazine. On the side, she is an official spokesperson for Botox.

Wang Junxia, runner

She never actually failed a drugs test, so depending on how you look at it, Wang Junxia is either one of distance running's greatest ever athletes, or its greatest disgrace. In September 1993, she won the 10,000m at the Chinese National Championships in a time that cut a scarcely believable 42 seconds off the previous world record. Three days later, she and another runner both broke the world record in the 1,500m. The following day, she broke the world record in her heat of the 3,000m, then broke it again in the final the day after. Never again did she or anybody else get close to these times, and after winning gold in the 5,000m at the Atlanta Olympics in 1996, the 23-year-old Wang retired, citing the way her health had suffered under her former coach Ma Junren's training methods.

In 2000, however, six of Ma's other runners tested positive for performance-enhancing drugs on the eve of the Beijing games, and ever since Wang's achievements have been tainted. She may have been almost impossibly brilliant, she may have been a drugs cheat, or she may have been the coerced victim of one, but we will probably never know. In her new life she founded a popular jogging club. Latterly, she even took up film acting. Her records still stand.

Andrew Ridgeley, musician

It is true that 23-year-olds who leave Wham! have only a 50% success rate. Yet it hardly seems fair to judge Ridgeley for failing to become a pop star twice, when once would be enough for most people. And at first, after the group's farewell concert at Wembley stadium in 1986, he didn't even try. Instead he moved to Monaco and took up Formula Three racing, without success. On his return to Britain, he recorded a solo album called Son of Albert, which flopped utterly.

Rather than embittering him, however, the experience seemed to get something out of Ridgeley's system. At the end of a hedonistic decade, he settled down with his partner Keren Woodward, herself a former member of Bananarama. The couple now live in quiet anonymity with their children on the north Cornwall coast, surfing, golfing and sometimes – you never know – popping to the shops. Thanks to his continuing royalties on Wham!'s music, Ridgeley is wealthy enough to need no other employment, and he is still just 50. Retirement indeed.

Sasha Grey, porn star

Given the way the industry has declined in recent years, Sasha Grey may ultimately be remembered as pornography's last great star. The American actor started in 2006, aged 18. She was known as much for her looks as for the extremity of the scenes she was prepared to work in, and the unusually thoughtful and assertive approach she took to making them. When she announced her retirement from the business on her Facebook page in 2011, it was with characteristic poise and wit. "It's become quite evident that my time as an adult film performer has expired," Grey said. "It was simply the perfect time for me to move on ... while I was on top (pun indeed, intended)."

And she has moved on. Having already starred in an experimental film directed by Steven Soderbergh, she became a regular character in the seventh season of Entourage on HBO. She makes music with an avant-garde pop band aTelecine, and in May, her first novel, The Juliette Society, is scheduled to be published.

Kim Clijsters, tennis player

Tennis players have a constant grind of tournaments to work through, which takes its toll. In 2003, Belgian Kim Clijsters became the first woman for 29 years to play more than 100 matches in a season, and afterwards had serious wrist, ankle and knee injuries to prove it. "I like to win and I put in a lot to do that, but the quality of life in and outside tennis are at least as important," she said, before having even won her first grand slam title. In 2007, aged 23, and with one US Open to her name, she retired – bringing the announcement forward, appropriately enough, because of injury.

After just two years, however, having got married and had a baby, she came back. Six months later, she had won the US Open again, beating both Williams sisters on the way to the final. The following year, she won it a third time, and then the Australian open in 2011, propelling her back once again to the top of the world rankings. If you are going to unretire, that is how to do it.