"There was a point about a year or two ago that things weren't going that great for me - I was just constantly on the grind and constantly getting nowhere," she says.
"My competitions were terrible and I couldn't put it together - it was a time where I was doubting myself, doubting my ability, and doubting whether I should actually be there."
But Holly’s never been one to quit.
She realised she needed to work through the slump, to keep getting up and going to training, and to reach out for help - from people like Para Athletics Lead Coach Raylene Bates, of Athletics New Zealand.
Then, in 2019, Holly threw a new personal best – and a new world best.
Her incredible 45.73m throw is the current world record for her class.
"Those highs and lows are part of sport, and they're part of what makes you the best athlete," she says.
"Coming out the other end and coming out firing was a really important point for me to realise that, actually, things don't always go well - things can be challenging … but you've got to stick in there and you'll get there at the end."
Holly says she has learned, over the years, to take setbacks like poor competition results, and use them as catalysts to develop resilience.
“Those competitions are things you can take very valuable things away from - but as a young athlete, I didn’t see it that way,” she says.
“I just saw them as a failure - I didn’t realise those are things I can really learn from - things that can make me a better athlete.”
Holly has faced not only her own internal doubts, but also the judgments of others.
“Growing up, I did have a lot of people that doubted me, and doubted my ability,” she says.