The world champions suffered a shock 1-0 opening Group F loss to Mexico that has put them on the backfoot ahead of their game against Sweden on Saturday in Sochi.
The Swedes won their opener against the Koreans and like Mexico have three points.
"The coach knows the situation that we are in now (is dire). (Every match is like a) final (from now on)," goalkeeper Neuer told a news conference, delayed by almost an hour due to ongoing team discussions. "We are frustrated and disappointed. Now it is up to us to react.
"We talked about what we must improve. We cannot change the result of the game (against Mexico) or of the warm-up games. Now we have to show what made us strong in the past. We are convinced we can do it."
The Germans had lost to Austria and narrowly beat Saudi Arabia with two unconvincing performances in their final warm-up games before arriving in Russia.
But instead of noticing the red flags and fine-tuning their game, they left their central defenders completely exposed to the speedy Mexicans, who took full advantage of it.
"No one is shying away from responsibilities. We have talked a lot. We have tried to find points that we can improve and say our opinions honestly," said Neuer, one of a group of players in the German squad who won the 2014 World Cup.
"The courage and the self-belief was missing. I cannot say why it was missing but from our body language and readiness of the past, it was not on the pitch."
Coach Joachim Loew has been sharply criticised for taking too long to react with substitutions but Neuer said it was not about making changes to the team that will face Sweden.
Defeat in that game could spell the earliest exit for the four-time champions since the 1938 World Cup.
"I am convinced we can show and will show a different face against Sweden. It is not very easy to just turn the switch. We have to work on it (both) on and off the pitch," Neuer said.
"We know the players on the pitch can deliver and take responsibility so for me it is more about readiness to play this tournament at 100 percent and not about personnel and changing players."
(Reporting by Karolos Grohmann, editing by Pritha Sarkar)
