Holders New Zealand are heavy favourites to defend the Webb Ellis trophy in the final at Twickenham on Saturday.
Australia have proved that Steve Hansen's side can be beaten, triumphing 27-19 in the Rugby Championship in Sydney in August.
That was the Wallabies' first win over their rivals since 2011, but New Zealand quickly responded with dominant 41-13 Test victory in Auckland a week later to retain the Bledisloe Cup.
But for Australia head coach Cheika the past means nothing, and his focus is purely on what is sure to be a pulsating 80 minutes.
"They say if you look backwards you are only going to get a sore neck. It really means nothing," he told a news conference.
"What's important is what happens in the next couple of days and the 80 minutes ahead of us. You see where you are and then see how the cards fall.
"I have got a lot of belief in the team. We had a short space of time between the Rugby Championship and this. We know it's going to be extremely physical and we have prepared accordingly."
Many pundits have pointed to Australia's excellent back row trio of Scott Fardy, David Pocock and Michael Hooper as key to their chances.
Cheika has been impressed with their cohesion, but insists there is better to come.
"I still think there is room for them to get better," he added.
"They haven't played that much together and they can still improve."