Resilience.
It is perhaps the "one percenter" athletes talk about that makes the difference between a good player and a great player.
On Friday afternoon, at the Australian Open in Melbourne, Jamie Murray, 35, is hoping to collect his eighth major title with partner Bruno Soares of Brazil in the men's doubles — 14 years after winning his first, the mixed doubles at Wimbledon.
His younger brother, Sir Andy, couldn't make it to Melbourne this year after testing positive to COVID, but he is expected to play in the three remaining 2021 grand slam events after a remarkable comeback from hip surgery that threatened to end his career in 2019.
Between them they have 10 grand slam titles and two Olympic gold medals, but the "one percenter" that puts them amongst the best in the world, and keeps them there, is quite possibly their mother's contagious attitude to life.
"Life is for living, you grab it with both hands, and you go after whatever you want to go after, and you make the absolute most of it," Judy Murray says.
Judy grew up in a small Scottish town where for the two weeks of Wimbledon every year, her mum gave up cooking and fed the children on a diet of as much tennis as they could consume.
Judy dreamed of one day being like Evonne Goolagong Cawley, the two-time Wimbledon champion who won a collection of other major titles in her own remarkable career.
"Yeah, I loved watching Evonne Goolagong when I was young. And in those days you only got Wimbledon on the TV … that was all the tennis that you saw," she said.
"Tennis was such a minority sport in Scotland back then — we had no indoor facilities, so you played tennis in the summer and something else in the winter.
"Nobody ever aspired to be a great player or a great coach — it just wasn't something that was going to happen."
But it did. Judy's days as Scotland's number one player morphed into coaching, eventually becoming Scotland's national tennis coach and, for a period, coach of the Great Britain Fed Cup team.
Next week she'll be addressing many of Australia's high performance coaches attending the From World Class To World Best conference organised by the Australian Institute of Sport.
It's been quite a journey.
She started in the small town of Dunblane, with a population of less than 10,000, offering free lessons to the local kids who eventually included two of her own.
Back then nobody imagined someone from Dunblane would become the first British major champion since Virginia Wade in 1977. Andy Murray took out the US Open in 2012 and put himself inside the "Big Four" alongside Novak Djokovic, Rafael Nadal and Roger Federer, who have dominated the male game for nearly two decades.
A year later, Andy won Wimbledon.
But in 1996 Dunblane made world news for another reason.
On March 13 in that year a local, Thomas Hamilton, shot 16 children and a teacher before turning the gun on himself inside the Dunblane Primary School gym.
Another 15 were injured.
Judy heard the news on the radio, trying desperately to get to the school along with every other Dunblane parent who had a child there.
For what must have seemed an eternity Judy did not know whether Andy and Jamie were among the casualties.
"It's coming up to the 25th anniversary … the boys were eight and nine at the time," she said.
"I was in the same situation as so many other mums in the town in that we were all rushing to get to the school when we heard that there had been a shooting. Of course, it was in the days before mobile phones.
"We had no information, we knew that there were police cars and ambulances in the school carparks but the gates were blocked and we were all waiting for hours and hours and hours before we actually found out what had happened.
"It was complete and utter disbelief that something like that could happen in our small town.
"You don't realise it immediately, but I think that in the few weeks after it happened, you become aware that life is so short, you never know what's around the corner.
"I could have lost my kids that day. Some of my friends lost their kids that day."
Judy went almost immediately back to the tennis club, giving Dunblane kids and parents a different focus.
"Life had to go on … so I think definitely it made me think, 'Whatever we want to do, let's just go and do it.'
"That was something you would never forget, never believed that you could have lived through something like that, but again, experiences form you, sometimes they change you as well.
"We never forget, but the town has moved on enormously and I think Jamie and Andy's successes in tennis have given everybody so much excitement, so much pride and connected the town with something happy and positive."
Her commitment to grassroots and community values remains as strong as ever.
Today Judy runs her own foundation, aiming to provide tennis infrastructure to every small Scottish town, while she continues to coach and mentor.
She lends her time to global programs like Sheroes, run by organisations including Tennis NSW, where women are encouraged to volunteer, as she once did, using sport to progress towards leaderships roles inside their communities.
And will she be guiding her grandchildren to become grand slam champions too?
"I'll never go through all that again," she laughs.
You get the impression, though, that she'd love nothing more.