Ferrari emerged as Mercedes' closest rivals at Albert Park, with four-time world champion Sebastian Vettel taking a podium in his first race for the team.
"If you are coming from a disaster like last year, the first race you want to be a bit more conservative because you still have the nightmare of last year on your shoulders," Arrivabene told Formula1.com.
"Now, Australia is gone, and it is time now to be a bit more aggressive."
Arrivabene also explained Kimi Raikkonen's exit, saying that a combination of pit crew error and the Finn being too eager to get away caused complications which ultimately led to his retirement, when his left rear wheel was not properly attached.
"There is something nice and something not very nice on the story," Arrivabene said. "Something nice is that Kimi was going like a rocket: everybody saw the timing of Kimi was unbelievable.
"The first pit stop he admitted he was [spinning the rear wheel a bit] and the mechanics had a problem on the tyres. We paid at the second pit stop, when the mechanical part of the tyres was broken. It was 50/50 - the guys put the car down too quickly, the light was still red, but Kimi looking at the car going down was operating on the clutch."
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