O'Neill won two gold among eight Olympic medals in the pool but admits her shock silver in her pet 200m butterfly event at the Sydney Olympics still stings.

The retired swimmer broke down live on radio last month while recounting that upset as she watched a replay of the race for the first time.

Speaking at Wednesday's Olympic uniform fitting in Brisbane, the former star known as Madame Butterfly admitted following her advice would be easier said than done.

"It's very difficult; training for a year, you've got one chance, one moment in time," she said.

"It's hard dealing with expectation as well, but by keeping perspective and doing your best you should be happy.

"But that's hard to do; it took me a long time to get over coming second (in Sydney)."

O'Neill won't be poking her nose into athletes' preparations in Tokyo but said she would set the tone now with a gentle reminder.

"You feel like you're never good enough to win and in my head I always thought people who won at the Olympics or did well were special people," she said.

"But then I became one and realised they're just the same as everyone else.

"You have to open your mind up to every possibility; there's a lot of upsets at the Olympics and it probably helps if you're not the favourite, to be honest."

O'Neill said she would heed the advice given by chef de mission Ian Chesterman once they arrive in Tokyo.

"He said 'there's nothing you can really do to improve their performance, but there's things you can do to really upset it'," she said.

"So I'm just there to mingle, be around and be someone they can talk to if they need to, not get in anyone's faces."

Australian Associated Press