He's witnessed the roller coaster of emotions in good times and bad.
And he's learned from it all.
The educational experience he gained as a player and a coach helped him provide the managerial leadership to take the Los Angeles Dodgers from last place in the National League West in late June to a division title, past Atlanta in the NL Division Series and into the NLCS -- which opens Friday against the St. Louis Cardinals at Busch Stadium (5:30 p.m. PT on TBS).
"Donny never panicked, kept his cool," said Pat Corrales, whose lengthy resume as a player, coach and manager now includes special assistant to Dodgers general manager Ned Colletti. "He never wavered, never complained. He didn't change."
At least publicly, that is.
"You know what they say," Mattingly said with a smile. "Fake it until you make it. There was a point I know I was close to being two hours from here [at home in Evansville, Ind.] long before now. "
There, however, was never a public sign of doubt on Mattingly's part.
He spent his playing career with the New York Yankees of George Steinbrenner, where turmoil was as constant as the morning sunrise. He was Steinbrenner's favorite player at times, and he was the brunt of Steinbrenner's ire at others.
He learned to ignore outside influences and keep a focus on the job at hand.
It has paid off handsomely in his managerial career.
Mattingly, the manager, had his doubters, and the number grew in the second half last season, when the Dodgers faded in the NL West race instead of overtaking San Francisco after acquiring Adrian Gonzalez, Josh Beckett, Carl Crawford and Hanley Ramirez.
Then, this season, with the signing of right-hander Zack Greinke and a payroll second only to the Yankees, the Dodgers were heavily favored to win the NL West. They stumbled early and woke up on the morning of June 22 in fifth place in the division, 9 1/2 games out.
That's when the cynics roared. They love to see the high-priced favorite fail.
That's when speculation began that Mattingly's job was in jeopardy. And that's when Mattingly won over those players in the Dodgers' clubhouse.
"He was in the middle of this whole season turning around," said Gonzalez. "He stayed consistent. He didn't panic or show anxiety. He was the same guy around us, and that consistency was important.
"He knew this team was good enough to win if we stayed with our game plan. One of the best attributes a coach or manager can have is not be afraid to lose his job. He had no fear."
It's a different world than the one Gonzalez suffered through in Boston last season before being dealt to the Dodgers in August 2012. There were a lot of expectations for the 2012 Red Sox, but there also were managerial and front-office distractions that carried over to the clubhouse and resulted in a last-place finish.
There were no such distractions in Los Angeles when the high hopes took an early blow. Mattingly wouldn't allow it.
"He was a great player, and he knows how tough the game can be," said Hanley Ramirez. "He gave us a lot of confidence. He kept everybody loose, because he didn't change. Everybody was upset. We felt we had to do something for him. We couldn't let him down."
The Dodgers did plenty. Saddled with a 30-42 record on the morning of June 22, they went on a 42-8 binge -- not once losing back-to-back games -- and moved into first place in the NL West on July 22. And on Sept. 19 in Arizona, they became the first team to clinch a division title.
Rookie outfielder Yasiel Puig was credited with infusing enthusiasm when he was called up from Double-A on June 3. Ramirez finally got healthy enough to see some regular playing time and was considered the foundation of the offense, finishing second on the team in both home runs (20) and RBIs (57) and hitting a team-high .345 despite being limited to 86 games.
And Clayton Kershaw and Greinke gave the Dodgers as dominant a left-right rotation combination as anyone in baseball.
The bottom line, however, is Mattingly's leadership -- the most critical aspect of managing, although often obscured by overreaction to in-game moves that are more about a player executing than a managerial decision.
"We went through a tough stretch, and he was himself through it all," said Colletti. "He was so steady. You couldn't tell when you saw him if we had won or lost.
"When you have talent and you are steady and show patience, you will be rewarded."
Mattingly has the patience.
And now he is enjoying the reward.