Imagine being at the top of your game, doing what you love – and then abruptly walking away.

Diana Nyad, the long-distance swimmer who set world records in the 1970s, did just that. From 1969 to 1979, she was arguably the world’s greatest long distance swimmer, breaking numerous men’s as well as women’s records. On August 22, 1979, Nyad set an open sea record for both men and women by swimming 102.5 miles from Bimini in the Bahamas to Jupiter, Florida without a shark cage. That day was her 30th birthday – and her last competitive swim.

For 30 years she didn’t swim a single stroke.

Speaking about it in 2010, Nyad said  “I was so burned out. You couldn’t pay me to take one more stroke.” But 30 years later, she had a change of heart and mind. “I was having an existential crisis about being 60,” she said. “I told myself, ‘You have to get real with life’s lessons, one of which is, you can’t go back.’ ” But, she realized, she could in a way go back – by going forward to complete her dream swim between Cuba and Florida. In 1978 she had attempted the 103-mile journey from Havana to Key West, using a shark cage. After almost 42 hours though, Nyad had to stop: she was so far off course due to high waves and strong currents that completing the swim would have been impossible.

The distance per se would not be the goal this time: she’d already successfully completed that open-water swim of almost 103 miles in 1979. The goal was finishing what she’d started in 1978, but upping the ante in two ways: 1) going slightly farther than she did in 1979, this time not with favorable winds and currents, but through strong shifting currents and 2) swimming through those shark-filled waters without a cage.

Training for this swim would test far more than her physical endurance – it would test her mental toughness, her resolve, her ability to find that razor’s edge between realizing your utmost, fullest capabilities and accepting limits.

• In 2010, after slogging through the bureaucratic processes and frustrating delays to get the permission of both the US and Cuba to make the swim, bad weather and cooling Gulf waters caused her to postpone the swim to the following summer.
• In 2011, strong currents and winds pushed her off course, she developed shoulder pain, and was stung by jellyfish. The stings caused her asthma to flare up, and 29 hours into the swim, she had to abandon the effort.
• In 2012, she sustained many jellyfish stings again which partially paralyzed her, and bad weather pushed her off-course, but it was a severe lightning storm that made it extremely dangerous to be swimming that caused her to make the hard decision to end the swim.

Three is usually the magic number for trying. Three long-term trainings, three attempts: Nyad had clearly demonstrated her physical strength, grit, and perseverance. No one at all would have blamed her for retiring the quest. She even said at the time that she would not make another attempt.

Amazingly, unbelievingly, she determined that she would try one more time.

Nyad returned to the waters off Havana two days ago, armed against jellyfish with a protection suit and a specially-fitted protective mask. Her pace has been steady: her friend Bonnie Stoll reported on Good Morning America this morning: “Diana started at 51 strokes per minute and right now she is doing 51 strokes per minute.” She has already far surpassed the 80 miles that Penny Palfrey swam on this route in 2012. She has had some problems with vomiting, is slurring her words due to dehydration, and her doctors are concerned about her lungs. But she is focused and determined.

Diana Nyad is, as I post this, swimming her last mile, and is on course to swim a total of 112 statute miles – 35 more miles than anyone ever before, according to her team. But the distance that she has traveled deep inside herself to find the motivation, discipline, and perseverance to make this journey is immeasurable, and is the real victory.