Germany coach Jurgen Klinsmann urged his players to "keep their feet on the ground" after their 3-0 win over Ecuador in Berlin on Tuesday.
The victory ensured that the hosts finished top of Group A.
"The team know if we play to our full potential we need fear no one, but we must keep our feet on the ground," 41-year-old Klinsmann said.
"We won't be allowed a single mistake in the games coming up. The tournament is up and running in earnest now."
Klinsmann added: "The goal of group winner is achieved. I am happy to sample the great atmosphere and with the points we have racked up but we must keep our feet on the ground."
The former Germany striker also said he was "not in the least bit bothered" whether his side next faced England or Sweden in the last 16.