At the age of 47, golf pro Phil Mickelson is playing some of the best golf of his winning career. Entering the 2018 Masters at Augusta National, Mickelson is driving the ball 10 yards farther than he did five years ago, and longer than many of the younger stars of the game.

Mickelson credits Tiger Woods for his longevity. While Tiger's not in the gym with Mickelson, Tiger's in his head--and that makes all the difference. "This is another effect that Tiger had on the game of golf as far as being aware of fitness," Mickelson told the Wall Street Journal on Wednesday. "It has allowed me to elongate my career."

Mickelson admits he doesn't love losing to Woods--Woods has 14 Major victories; Mickelson has five--but he loves the challenge of playing against the best. At a press conference ahead of the Masters, a reporter suggested Mickelson would have won more tournaments had he played in an era without Woods. Mickelson corrected him:

"He [Tiger] brought out the best in me and forced me to work harder and focus to ultimately achieve the success that I've had...I've appreciated the challenge of playing and competing against him, and I also appreciate the level of greatness that he's achieved in his career."

Mickelson has what Stanford psychologist Carol Dweck calls a "growth mindset." In her book, Mindset: The New Psychology of Success, Dweck writes that your beliefs "profoundly affect the way you lead your life."

People with fixed mindsets are non-learners. They believe their intelligence, talent or skills are fixed and can't be developed much. Those with growth mindsets, on the other hand, are always learning, growing, challenging themselves and looking for opportunities to stretch themselves.

Above all, growth mindset leaders seek out opportunities to be surrounded by people who are better than they are. The billionaire Warren Buffett once said, "It's better to hang out with people who are better than you. Pick out associates whose behavior is better than yours and you'll drift in that direction." While Mickelson didn't choose to hang out with Woods for his career, he sees the rivalry as positive.

Mickelson's "misfortune" is actually his strength.

Whenever Mickelson is asked about Woods, he takes the opportunity to show the rest of us what a growth mindset sounds like.

At the 2017 PGA Championship at Quail Hollow in Charlotte, North Carolina, Mickelson was asked during a press conference what he thought about the "misfortune" of playing against Tiger Woods for much of his career. Once again, Mickelson's answer was pure growth mindset:

"I feel as though had Tiger not come around, I don't feel I would have pushed myself to achieve what I ended up achieving, because he forced everybody to get the best out of themselves."

That's eerily similar to a quote from Dweck's book: "People in a growth mindset don't just seek challenge, they thrive on it. They bigger the challenge, the more they stretch."

Dweck believes anyone can cultivate a growth mindset--and her research shows that learning about the growth mindset is the first step to developing the winner's edge. Sure, it can be frightening to give up the notion that you're the best. It can also propel you to new heights.

We all have fixed and growth components rattling in our brains during the day. For example, if you're thinking about accepting a new challenge in your business or career, your fixed mindset will whisper, "Don't take it on because you'll fail and you'll be exposed as a fraud."

According to Dweck, you don't have to listen to it. Instead, take action on the growth mindset which shouts, "Let's do this thing. I'll learn and I'll grow from it."

The next time you hear sports fans praising a champion athlete, listen for the growth mindset. It's always playing a role behind the scenes.