The Netherlands, the 2010 World Cup runners-up, began their World Cup trip with a stunning 5-1 victory against Spain in the Group B opener. (Agencies)
However, Van Gaal just regarded it as the first step for Netherlands to the trophy.
"We haven't made it to the next round yet so anything can happen," Van Gaal said.
"You win the World Cup by winning the final, we shouldn't get ahead of ourselves,” he added.
Van Gaal was relieved that the experienced players already set an example to ask the youngsters to keep their feet on the ground.
"They know what is going on and they warned the team last match was simply one victory and that we haven't won anything," said Van Gaal, who will be the manager of Manchester United after the World Cup.
The Netherlands will face Australia in Porto Alegre June 18. Van Gaal hinted that he will change formation from 5-3-2 to 4-4-2.
"If Australia is going to play a very defensive match then 4-3-3 will allow us to put more pressure on them up frontm” Van Gaal said.
"We need to prove our capability to win over Australia, which won't be that easy," he added.
The Netherlands are yet to beat Australia in three previous friendly matches with two draws and one defeat, which were played between 2006 and 2009.
The Netherlands, the 2010 World Cup runners-up, began their World Cup trip with a stunning 5-1 victory against Spain in the Group B opener.