The world motocross rider is well versed in disappointment. She has had more setbacks in three seasons than most will experience in their careers.
But until now the Palmerston Flyer has always been able to shake off the frustration with her constant positivity and steadfast confidence.
But weeks and weeks of hobbling around in a moon boot or with a crutch in one arm has left the bubbly 22-year-old feeling flat.
Watching Italian Kiara Fontanesi collect the Women's Motocross World Championship title - her sixth in seven years - was extremely difficult.
"It was tough to watch, especially when I felt it was really mine," Duncan told the Otago Daily Times.
"I'm not going to lie - this has definitely been the toughest one.
"We can learn from this, I guess. Most importantly, I need to put all this [rubbish] behind me and tell myself everything is going to be all right and keep going."
Duncan had built a huge 21-point lead over her two main rivals, Fontanesi and Dutch prospect Nancy van de Ven.
She almost could have coasted to victory but was forced to pull out of the series with four races remaining when an injury to her right foot proved much worse than initially thought.
"This year I felt like I had really worked on my weaknesses that let me down last year. It was heartbreaking to go out like that."
It was the third consecutive season Duncan's chance at glory were cruelly snuffed out.
Last year a contentious jury decision stripped her of an opportunity to claim the title, while in her rookie year she crashed into a stray photographer who had got in the way.
Duncan does not require surgery for her foot but she has ruptured a ligament and is still experiencing pain.
"The pain is not too bad. But I haven't been able to walk properly for a long time and everything is just weak," she said.
"It is still going to be at least eight weeks before I can get on a bike. It is a really long time but it is important that I take the time so it can heal properly.
"I'll soon be back on the bike doing what I love," she said.
One immutable truth keeps Duncan going through what has been a trying period - she has been the fastest rider in the championship during the past three years.
"I'm going to have wait another year but I'm pretty stubborn. This injury hasn't knocked my confidence.
"I haven't once questioned my ability. I've never questioned that - I know I can do it.
"It is just the getting-it-done-type part which I have to get to now."
Duncan knows how to return from setbacks but dealing with the disappointment has been more exhausting this time around.
"The highs are so high and the lows are so low. It is difficult because you love it and you are so passionate and it is everything to me, so it has been hard to handle.
"As hard as it is, you have to stay neutral and not let those lows get too low or the highs get too high, because I know better than anyone how quickly it can turn, and in a heartbeat.
"You have to find your level and hold that faith, I guess."
Duncan said she would be lost without her close friends.
"You really realise who is there for you and how good those people are when you go through those tough times.
"Everyone wants to be there when you're winning. They all want to be there and part of it.
"But when you are going through tough times, the ones who pick up the phone I'm thankful to have, not only in my sport, but in my life."
