The Italian emphasised the need to learn from the errors that led to the hosts' stunning second-half comeback as he prepares his squad for next year's World Cup in North America.
Ancelotti, who took charge in May following Brazil's inconsistent World Cup qualifying campaign, has focused on building a team that is both adaptable and mentally robust.
Despite showing signs of progress in recent matches, Tuesday's defeat highlighted areas requiring improvement and called into question the coach's decision to field a heavily rotated side from Friday's commanding 5-0 win over South Korea.
"No, everything is not fine. When the team loses, we are upset, which is normal. Everyone is upset. I don't like to lose, and neither do the players. We have to learn from this defeat, as we always do in football," Ancelotti told a press conference.
"Until (Fabricio) Bruno's mistake on the first goal, the game was well controlled. After that, the team fell apart mentally. That was the team's biggest mistake," he said.
"I don't think the second half was bad overall, but the error had too much of an impact on the players."
When asked if such mistakes could influence squad selection for the World Cup, Ancelotti dismissed the notion, instead focused on the team's collective response.
"Individual mistakes do not affect a player's presence in the team. What we have to evaluate is the team's reaction after the first mistake, which was not good because we lost a little of our balance on the pitch, and our positive thinking. It's a good lesson for the future," he said.
Brazil's next fixtures are friendlies against Senegal and Tunisia in November, to be played in England and France, respectively.
"This and the next international break are testing periods, and we will continue testing in November," Ancelotti said.
"The team played very well against Korea, well in the first half today, and very poorly in the second half.
"In the World Cup, we have to strike a balance. We must learn from our mistakes. It was a good lesson tonight. I think we need to find a balance in what we do. It's a process..."