The former defender was in the starting XI as the Selecao crashed to a humiliating defeat on home soil in the World Cup semi-final and admits that the nature of the loss was a "disgrace".
In an interview with FourFourTwo magazine, Marcelo said: "It was a horrible feeling, the worst that I experienced in my entire career.
"To lose that way was a disgrace. Playing a World Cup in your own country, defending your national colours, with all your people around you, and the losing 7-1 was indescribably painful. It was madness – no-one could believe it. The fans were sad, but so were we in the dressing room."
However, the former Real Madrid player says the defeat forced him to come back stronger.
Marcelo said: "I rose from that. I told myself I didn't want to be left with that bitter taste. Sometimes in life, a defeat serves as a push to improve, and I think from that night against Germany, I came out stronger.
"Maybe if we'd reached the final and won the World Cup, my mind might have said, 'Enough', and I would have said goodbye to football. Luckily, I never lost my motivation."
Marcelo won the Champions League on five occasions during his time at Real Madrid and described his final triumph in 2022 as the most special, even though he didn't play as much during the campaign.
The full-back – who spent 15 years with Los Blancos – said: "I felt important that season, despite losing prominence and playing less.
"I helped the younger players, stayed close to (Carlo) Ancelotti and made it clear to him that I understood why he preferred other players in my position. It was like saying to the coach, 'Don't worry, I'm with you, I'm not going to cause you any problems.'
"I always wanted to play, even in kickabouts with my kids, because I'm a winner. But I also felt helpful advising Federico Valverde, Eder Militao and Vinicius, and sticking together with the more experienced players like (Toni) Kroos, (Luka) Modric and (Karim) Benzema."