England opener Alastair Cook has admitted playing Australia is "more intense" than against other teams.
We've got to believe we can do it - if we don't believe it, no-one else is going to either
Alastair Cook on the third Test
"You notice it physically at the end of the day, you feel like you've been in a battle all day.
"They keep coming at you from the first ball to the last," commented Cook, who is playing in his first Ashes series.
England are 2-0 down with three to play but he said: "Cricket is a strange game and it can change very quickly. That's what we've got to believe."
Cook's highest score in the series so far is 43 but he is happy with his form and warmed up for the third Test by hitting 106 against Western Australia.
"The two-day practice game was very good for a lot of people and they got a lot out of it.
"We can't sit around sulking any more, we've got to come out again in Perth and fight again . Hopefully this time the result will be different," he said.
The odds will be against England at a ground where they have only won once in 10 previous Test matches - the sole victory coming in 1978 against an Australia side minus its star names because of Kerry Packer's World Series.
"We've got to believe we can do it - if we don't believe it, no-one else is going to either.
"Only we can get out there and do something about it and we're going to stay as confident as we can. It's going to be tough, there's no denying that, but this is where we stand up and have a real fight," Cook continued.
Australia have enjoyed some success against the 21-year-old by bowling round the wicket at him, but he has been working hard to combat that tactic.
"It has been slightly different, but I've reacted to that and done a lot of practice on technique and studied it as well," he said.
"I have to make sure the alignment of the body and feet is the same for over and around the wicket.
"We get the net bowlers coming around the wicket and make sure the throw-downs are all from around the wicket for that extra bit of practice," he added.