When she was growing up, Caroline Wozniacki hated losing any sort of contest, especially to her older brother Patrik.
Whether it was tennis, soccer or even a board game, the very thought of letting him brag about it for the next week was too much to bear. She just had to win.
The world No.2 believes this family-entrenched fighting spirit helped her complete one of the great comebacks of her career, storming home to defeat little-known Croatian Jana Fett and keep her Australian Open dream alive.
Wozniacki saved two match points when trailing 5-1 in the third set, then proceeded to win 23 of the next 30 points to ultimately prevail 3-6, 6-2, 7-5.
"If you lose a game to anyone in my family, you're going to hear about it for at least a week," she said with a smirk.
"Growing up, I never wanted to lose and the worst to lose to my brother. Giving him the opportunity to be ahead to be able to talk shit to me was not pleasurable," she added, laughing.
"So I think from that point you just learn and fight and you don't give up, even if it's a board game or tennis or soccer or whatever it is."
The difference in experience at grand slam level was evident as things got tight in the third set, with Wozniacki appearing in her 43rd main draw, compared to Fett who was making her grand slam debut.
While Fett was visibly nervous in trying to close out the match, Wozniacki was battling her own demons, given she had previously been eliminated from four grand slams by opponents ranked outside the top 100.
But the Dane's killer instinct kicked in, becoming more aggressive with every point as the match went deeper into the deciding set.
"I felt her tighten up just slightly and I just thought to myself, you know what, at this point ... don't give it to her.
"She's about to beat the No. 2 player in the world, that's what I was thinking and obviously she's about 100 in the world, so that's a big moment for her.
"I know how it feels whenever you're close to reaching something really big and I felt like I was going to get the opportunity, maybe, if I got to 5-2."
With seeded players dropping like flies in the women's draw, Wozniacki looked well on her way to joining the scrap heap half an hour into the match, losing the first set 6-3.
But the former Australian Open semi-finalist found a foothold in the match and was able to take the second set 6-4 to even the ledger.
But, after holding serve in the opening game of the third set, Fett grabbed the match by the throat, breaking Wozniacki twice and winning the next five games to serve for a spot in the third round.
She then had two match points at 40-15, and looked to have sealed the victory with an ace but it was called out and Fett opted not to challenge.
From there, Fett hit four unforced backhand errors to give Wozniacki advantage, before the Dane hit a forehand winner to seal the break.
After that point, the 21-year-old Croatian, who began the 2017 season ranked 325, could manage only seven more points as her vastly experienced opponent could smell blood.