The thing Pettitte struggled with, the thing he never really could wrap his mind around, was that he was finished with Major League Baseball. He was still pitching at a high level when he walked away after the 2010 season.
As much as Pettitte wanted to be one of those guys who went out on his own terms, he was never completely satisfied with his decision. He'll tell you he loves his life with his family, and I'm sure he does.
Pettitte is a man of honor and a man of faith, and he desperately wanted to be closer to his family. He also believes God gave him incredible athletic gifts and saw part of his mission as using those gifts. His ministry was to live a very public life a certain way, to be the right kind of man.
Last summer, Pettitte was telling former teammates that he was really, really happy in retirement, but that he would have to re-evaluate baseball after the season and see if he was up to returning.
Some of those teammates were convinced Pettitte hadn't pitched his last game. One of them, Lance Berkman, began recruiting him for the St. Louis Cardinals.
That wasn't ever going to happen. If Pettitte was going to return, he was going to pitch for the Yankees. He understands and embraces the history of the Yanks, and he was proud to have played a part in five World Series championship teams.
Still, when the offseason came and went with Pettitte staying retired, there was a feeling that maybe he wouldn't try again after all. Maybe he really had settled into a life away from the game.
And then on Friday morning came the news that Pettitte had decided to try to pitch a 17th Major League season, 14th with New York.
It'll be fascinating to see how quickly Pettitte can be ready to pitch in a game and how good he'll be when he does. The Yankees have CC Sabathia, Ivan Nova, Michael Pineda and Hiroki Kuroda penciled into four spots, and Phil Hughes and Freddy Garcia competing for the other two.
Still, if Pettitte has anything left in the tank, he'll get one of the slots. The Yanks have seen him pitch too many big games to pass up a chance to take advantage of his experience and savvy.
Joe Torre often said the most important game in this run of five World Series championships was Pettitte's brilliant performance in a 1-0 win against John Smoltz and the Braves in Game 5 of the 1996 World Series.
Pettitte was always at his best when the stakes were the highest. His focus seemed to wander during the regular season, and it irritated George Steinbrenner more than a little.
But Pettitte's return means the Yankees just got smarter and tougher. They got an infusion of character and poise, too. In fact, if you were to make a list of all the intangible things good teams have, Pettitte would check off almost every box.
That's the thing people don't know about him. They think because he's so quiet and so nice that he's just along for the ride. They don't see his inner toughness and his relentless drive because he has chosen not to reveal them.
Pettitte's teammates know. They've always known. They've admired him and followed his example in terms of work ethic, professionalism and being at his best when the games count the most.
Yes, Pettitte has admitted to using human growth hormone. He said he was injured and scared in 2004, and he made a terrible mistake. When you think of Andy Pettitte, I'm guessing performance-enhancing drugs are not the first things that come to mind.
Derek Jeter and Mariano Rivera have to be thrilled that Pettitte has decided to resume his Major League career. Brian Cashman and Joe Girardi must surely feel the same way.
They were there for all or most of Pettitte's 13 seasons with the Yankees, and they know what he meant to those clubs, not just in terms of production and innings and big-game presence, but also in composure, work ethic and doing things right.
Roger Clemens was widely credited with instilling a tougher work ethic in Pettitte, but Clemens has said that they drove one another.
"Don't sell Lefty short," he said.
What we don't know, what we really can't know, is how much Pettitte, at 39, has left in the tank. He was plenty good when he went 11-3 with a 3.28 ERA in 21 starts two seasons ago.
For several years before that, Pettitte was torn about whether to continue his career. He didn't need the money, and he appreciated the time with his family.
He tried to have it both ways during those three seasons with his hometown team. The Astros showed him the door after the 2006 season, but the truth is that Pettitte was always a Yankee.
He understood why wearing pinstripes is special and how lucky he was to be identified with Jeter, Rivera, etc. They'd come to the Majors at about the same time and they'd led the Yankees on one of their great runs.
Now they're together for one more run.
Richard Justice is a columnist for MLB.com. Read his blog, Justice4U. This story was not subject to the approval of Major League Baseball or its clubs.