The Germans crushed hosts Brazil 7-1 in last night's semi-final and Neuer has insisted that they must "start again" despite their historic display.
"Now it's very important for us to keep calm," the Bayern Munich stopper said.
"It's important for us to not just think that we can beat every team in the world easily, especially as the next game is the final, when we will come up against the best in the world.
"We have to start again. We need to work hard. We must remember that it is not important what we did in the semi-final."
Germany will face the winner of tonight's semi-final between Argentina and Netherlands in the Rio de Janeiro final on Sunday.