A Fernandinho own goal and Kevin De Bruyne strike helped Belgium to a 2-1 victory in Kazan, where Roberto Martinez's men held on despite Renato Augusto's second-half header.
"I didn't expect that, I expected more difficulties, but we were so organised collectively," he said after the win.
"I always had help from Marouane Fellaini, from Toby Alderweireld. We were really focused on him, on [Philippe] Coutinho, on Marcelo, and we did a really wonderful job. I think we can congratulate ourselves for the job that we did defensively.
"Even offensively I got really frustrated because I didn't touch the ball. I made a lot of sacrifices for the team and I am happy that we won because of that."
The win helped Belgium move into a first World Cup semi-final since 1986, with a clash against France awaiting them, although Meunier will miss through suspension.
Fellow Belgium defender Jan Vertonghen believes Didier Deschamps' men will provide a tougher test than Brazil.
"I think France are a bit more complete than Brazil are," he said.
"I think it will be harder to break them down."
That semi-final match up will take place July 10 at the St Petersburg stadium.