The lessons, however, keep on coming.
The former biology teacher and high school principal is now a full-time horse trainer, and his favorite pupil is heading to the Kentucky Derby.
General Quarters roared past leader Join in the Dance at the top of the stretch, then held off favorite Hold Me Back by 1½ lengths to win the $750,000 Blue Grass Stakes on Saturday and Keeneland and stamp his 75-year-old trainer as the feel-good story for next month's Derby.
It'll be a homecoming more than 40 years in the making, one McCarthy finally knew he'd have when jockey Eibar Coa nudged the 3-year-old colt on the turn and told him it was time to get moving.
"That's his signal, that's what we've taught him," McCarthy said. "When he asked him to go, he just went."
General Quarters covered the 1 1/8 miles on Keeneland's Polytrack in 1:49.26 and paid $30.60, $11 and $7, setting off a raucous celebration in the winner's circle.
"We're going to the Derby! We're going to the Derby, yeah!" said Mike Adams, McCarthy's son-in-law. "It's going to be big. It's huge. We're all overwhelmed. This is very surreal."
It certainly seemed that way as McCarthy made his way through the grandstand. When the crowd rose to give him a standing ovation, McCarthy tipped his cap and struggled to fight back tears.
McCarthy spent most of his teaching career training horses in the pre-dawn hours before heading to school. He had a 3-year-old nominated to the Triple Crown back in the 1960s, but the horse whose name McCarthy can't even remember died.
He's scratched out a modest living since going into training full-time in 1990. General Quarters purchased for a meager $20,000 last year is the only horse he currently has in training, one McCarthy didn't give up on even after a tough fifth-place finish in the Tampa Bay Derby last month.
Instead, McCarthy who does everything from hotwalk to bathe his rising star sent General Quarters home to Churchill Downs and went back to work. The colt put together a blistering five-furlong work last week that told McCarthy all he needed to know.
"I never lost faith in this horse," McCarthy said. "I'm with him every day five or six hours, watched him train, figured out his schedule. I knew at that time I had him right where I wanted him."
So did Coa, who deftly guided General Quarters through the 11-horse field. Knowing his mount didn't like dealing with heavy traffic, Coa pushed General Quarters early just off the shoulder of Join in the Dance. He stalked the leader on the backstretch and made his move at the turn, pulling ahead at the top of the stretch then digging in when Hold Me Back started to close.
"He was very professional today," Coa said. "He showed today he's going to be ready for (the Derby)."
The same can't be said of Mafaaz.
The English horse has already earned a spot in the Derby after winning the Kentucky Derby Challenge Stakes at Kempton Park outside London last month.
Trainer John Gosden entered Mafaaz in the Blue Grass to see if he could match up with his North American brethren. Mafaaz never challenged, finishing eighth and jeopardizing his chances of running at Churchill Downs.
"I was a little disappointed," Gosden said. "I thought there might be a bit more pace. We're going to have to regroup and see where we're at."
Hold Me Back has no such worries. Though he couldn't duplicate the spectacular move that carried him to victory in the Lane's End last month, jockey Kent Desormeaux hardly seemed bothered.
"I wanted to make sure he got tired, but I can't make him tired, he's too fit," Desormeaux said. "You're most likely to win the Belmont, but you're going to win the Derby."
Charitable Man, making his first start in seven months after suffering a saucer fracture in his shin, finished seventh. One of the top 2-year-olds in the country before getting hurt, Charitable Man's status for the Derby is up in the air.
"When I called for him to run, he didn't respond," said jockey Alan Garcia.
Theregoesjojo, a distant third to Quality Road and Dunkirk in the Florida Derby last month, led early but faded to ninth.
Patena, owned by IEAH Stables and trained by Rick Dutrow the combination behind last year's Derby and Preakness winner Big Brown was 10th.
Dutrow and IEAH stormed the Derby last year, creating one of the largest and brashest winner's circle victories in recent memory at the Derby.
The crowd could be even bigger, if not quite as rowdy, if General Quarters can summon another remarkable finish under the twin spires in three weeks.
It's a moment McCarthy and his family have waited decades for, one he's kept at even when the odds were stacked against him.
"He's got some knocks along the way, then he just gets right up and goes right back," said McCarthy's wife Patricia. "He has a lot of determination."
Now, he's got the horse to match.