The last time Keeth Smart appeared on the Olympic stage, he was left weeping in front of television cameras from around the world. As he returns to the Games four years later, the greatest challenge for the captain of the American men’s sabre fencing team is to keep his emotions at bay.

“With fencing, you can never let your emotions take over, because then you’re going to make fatal mistakes,” Mr. Smart said. “Still today I’m learning to stay controlled, but it’s not easy.”

“He gets angry, and he cannot get angry,” his coach, Yuri Gelman, said. “When he gets angry, he is basically just running and trying to win, and that’s not his style, and he’s losing in this situation.”

Putting his emotions aside will be no easy task for the 30-year-old lifelong New Yorker. In the past four years, Mr. Smart has endured the deaths of both his parents, physical ailments that almost kept him out of the Games, and the weight of the memories of his experiences at the 2004 Athens Olympics.

It was there that he lost two medal opportunities, each by only a single point.

“At the time, I thought it was the worst thing that could ever have happened to me,” Mr. Smart said at his Midtown training club. “Like I was being punished, or I was cursed.”

Afterward, he took more than a year off from the sport — “to clear my head,” as he put it. Upon returning to the fencing arena, he experienced even more adversity.

First, his father — who first introduced him to fencing at age 11 — died. In February, he tore a ligament, putting him out of commission for a month. In April, he contracted a rare blood disorder, hospitalizing him and benching him for two more months. In a way, the cure was worse than the disease; he was put on a steroid-based medication, very nearly barring him from competition.

Then, less than two months ago, as he began the final training stages for the Olympics, his mother died.

The Brooklyn resident is about to compete in his third consecutive Olympics. After beginning his career at Manhattan’s Peter Westbrook Foundation, which brings underprivileged children into fencing, he attended Brooklyn Technical High School. He then received a scholarship to attend St. John’s University, where he twice won the NCAA title.

While still in college, Mr. Smart went to the 2000 Sydney Olympics. After graduation, he continued to fence, but also took up a full-time job in corporate finance. Perhaps his most famous achievement in the fencing world came in 2003, when he became the first American male to be ranked no. 1 in his sport.

“He’s a celebrity, as close as you can get to that in fencing,” his youngest teammate, James Williams, who grew up watching Mr. Smart, said.

Off the strip, Mr. Smart wears a wide, toothy smile and punctuates his conversations with deep belly laughs. But sabre fencing, by definition, requires a certain degree of aggression, especially when compared to the two other fencing events — foil and epee, which rely on touching opponents with the tip of one’s sword.

“Sabre is basically the former cavalry sword,” another teammate of Mr. Smart’s, Tim Morehouse, said. The target is the upper body and the head, and one can use the whole sword for a point. “You’re making slashing actions, so the idea, I guess, with the upper body, is that you would want to kill the person, not the horse,” he added.

During training at the Manhattan Fencing Club, it’s easy to see how Mr. Smart would excel in such an event. With his long legs, he leaps forward at his sparring partners with sweeping lunges, before darting back.

At his side is the rest of the team: Mr. Morehouse, Jason Rogers, and the alternate, Mr. Williams.

They have rarely competed as a full team, joining mainly in qualifying events. Individually, they have had a rough few months. At a high-profile tournament in Las Vegas on June 22, all the team members except Mr. Smart were knocked out in the first two rounds, and Mr. Smart squeezed by for a fifth-place finish.

Nevertheless, Mr. Smart is ranked in the top 10 for overall competitions and Messrs. Morehouse and Rogers are in the top 25.

As their August 3 arrival in Beijing approaches, Mr. Smart acts as a model of stability for his compatriots as they enter the pressure cooker of the Olympic stage. “We all look up to Keeth,” Mr. Rogers said. “He’s a seasoned veteran.”

After the Games, he will leave the sport. The many obstacles he’s had to deal with have weighed on his decision. “I think God is sending me a sign that it’s time to stop,” he said with a laugh.

Then, it’s off to the world of business. Building on his old finance job, he will be starting at Columbia Business School in the fall.

When quarterly reports and balance sheets come down the pipeline, the most crucial of his fencing strategies — staying calm — is a big help. “Some of my colleagues and co-workers would get so worked up and stressed out,” he said. “I’m able to keep things in perspective.