Nursing a rivalry — whether it's with a colleague, a friend or a sibling — sounds stressful, but the right kind of competition can be a powerful motivator, and push us to be better.

• Case in point: Carlos Alcaraz and Jannik Sinner, the top two tennis players in the world, faced each other in three Grand Slam finals this year, including most recently at the U.S. Open, where Alcaraz took home the title. "They have one of the most electrifying rivalries in sports, and their duels — fast, fierce and breathtaking — seem to push each other to new heights," The New York Times' Simar Bajaj writes.

💰 The money quote: "Your biggest rival can actually be your greatest ally," Adam Grant, organizational psychologist at Wharton, told Harvard Business Review's IdeaCast.

Zoom in: Research has shown how rivalries can have perks.

• In one study, NYU researchers found that runners ran about 5 seconds faster per kilometer in a race when someone they considered a rival was also racing.
• An analysis of different NBA, NFL, MLB and NCAA team performances found that when a team's rival crushes it in the postseason one year, that same team goes on to do better next year.

But there are also situations in which rivalries can hurt us.

• Another study found that people may be likelier to be unethical or cutthroat when competing against a rival because they really want to win.

👀 Between the lines: One difference between rivalries that boost us versus those that bring us down is whether we're thinking about these as long-term relationships or not, the Times' Bajaj notes.

• Those who don't have the long view might get too tangled up in each win or loss against another person or team, instead of thinking about the rivalry as an ongoing competition that pushes both sides to new levels.

🤝 Zoom out: A key component of Alcaraz and Sinner's rivalry is their underlying friendship. "We are enemies when we step on the court. But it ends there after the handshake," Alcaraz said after Sunday's match.

• That mirrors psychologist Grant's advice: Be buddies with your rival. "We have some mutual respect, and so let's try to beat each other. But you know, the loser will buy the winner dinner, or we'll still root for each other and be glad that one of us won," he said on IdeaCast. "That's the pattern you want to get to."

The Manhattan skyline as seen at sunset from the Billie Jean King National Tennis Center in Queens last week.