"The greatest gift has been to be completely immersed in my passion and striving for something I loved so much -- visualizing a ladder, climbing up to my heroes," Nash, 41, wrote. "The obsession became my best friend. I talked to her, cherished her, fought with her and got knocked on my ass by her.
"And that is what I'm most thankful for in my career. In my entire life, in some ways. Obviously, I value my kids and my family more than the game, but in some ways having this friend -- this ever-present pursuit -- has made me who I am, taught me and tested me, and given me a mission that feels irreplaceable. I am so thankful. I've learned so many invaluable lessons about myself and about life. And of course I still have so much to learn. Another incredible gift."
Nash, who didn't play this season with the Los Angeles Lakers because of injuries, finishes his career with 10,335 assists, third-most in NBA history behind John Stockton and Jason Kidd.
"To now realize that it's over, it's really difficult to put it into words," Nash told ESPN.com's Marc Stein in a "SportsCenter" sit-down that aired after Nash's announcement Saturday.
"It's just a weird transition. Every athlete goes through it. A lot of people say an athlete dies twice, and in some ways, without being salacious, that's true. If you want to enjoy and be happy in life, you have in some ways to say goodbye to your former self. And that's not easy, especially for guys. We're not the most communicative of the species. So it's hard to kind of put it all in perspective."
Canadian Prime Minister Stephen Harper took to Twitter to congratulate the British Columbia product.
Nash is the most accurate free throw shooter in NBA history, edging Mark Price's career mark at 90.4 percent. And for nine straight seasons from 2001-02 in Dallas through 2008-09 in Phoenix, Nash quarterbacked squads that ranked No. 1 in the league in offense.
"When people ask me if I have a favorite game or play or moment on the court that stands out the most, I can't answer them," Nash wrote. "It all blends into one. What comes to mind are all the great teammates I've played with and the friends I've made through the years."
Despite several health struggles late in his career with the Suns, the Lakers gave Nash a three-year, $28 million deal in 2012 and mortgaged their future by shipping four draft picks to Phoenix.
But Nash's tenure in Los Angeles was mostly miserable.
He broke a bone in his left leg in his second game and missed the next 24 in 2012-13. Last season, more health issues sidelined Nash for all but 15 games. And because of back, knee and hamstring issues, Nash played in just 65 of a possible 164 regular-season games the past two seasons with the Lakers.
"When I signed with the Lakers, I had big dreams of lifting the fans up and lighting this city on fire," Nash wrote. "I turned down more lucrative offers to come to L.A. because I wanted to be in the 'fire,' and play for high risk and high reward in my last NBA chapter. In my second game here, I broke my leg and nothing was the same.
"Last spring, when I returned to the court, I was given a standing ovation at Staples Center. It was a dark time in my career and that gesture will be one of my best memories. There's been a lot of negativity online, but in my nearly three years in L.A., I've never met anyone who didn't show me anything but love and support for my efforts."
The Lakers, according to Nash, have "for all intents and purposes" regarded him as retired since late October, when it was announced that he would miss the entire 2014-15 season. The only reason Nash's retirement wasn't made official then, he said, was that Lakers general manager Mitch Kupchak asked him to delay the announcement until after the Feb. 19 trade deadline. That way the Lakers could explore the trade market and see whether they could acquire a future asset in exchange for Nash's expiring $9.7 million contract, which counts against the Lakers' cap.
"I could have medically retired," Nash told ESPN.com. "But they asked if I'd consider just being out for the year. ... Really it was about giving them an opportunity to move my salary and improve their team.
"For them to trade me to improve their team was something I was completely on board with. The organization's been unbelievable to me. ... How Mitch has treated me and the Buss family has been incredible. It was the least I could do."
Nash starred at Santa Clara before starting his NBA career with the Suns, who traded him to Dallas in 1998. He established himself as an elite point guard while playing for coach Don Nelson alongside Dirk Nowitzki and Michael Finley with Dallas.
"I remember when Dirk and I were nobodies," Nash wrote. "He used to say over dinner sometimes, 'How are us two stiffs gonna make it in this league?' Somehow we made something of ourselves. After all the wins and all the great times we've had around the world together, what really means the most to me are the late nights early in our careers when we'd go back to the Landry Center in Dallas, to play a few more games of H-O-R-S-E and one-on-one."
Nash returned to Phoenix in 2004 on a lucrative free-agent deal.
The 6-foot-3 Nash won consecutive but unlikely MVP awards in 2005 and '06 -- one of just 10 players to win in back-to-back years -- as the catalyst for one of the most prolific offenses in NBA history under coach Mike D'Antoni. His playmaking and scoring earned him worldwide recognition and eight All-Star Game selections, including his final season with Phoenix in 2011-12.
"It will always hurt that Phoenix Suns fans didn't get the championship they deserved during our run," Nash wrote. "Yes, we had some bad luck but I always look back at it and think, I could've made one more shot, or not forced a turnover, or made a better pass. But I don't regret anything. The arena was always sold out and rocking. It was the time of my life. Thanks, Phoenix."
Nash said in his letter Saturday that he likely will never play basketball again.
"It's bittersweet," he said. "I already miss the game deeply, but I'm also really excited to learn to do something else."
Marc Stein of ESPN.com contributed to this report.
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