"The players showed they had faith and belief until the very end," the 62-year-old is quoted as saying by BBC Sport following the game.
"The humidity was not in our favour so when you see that until the very last minute we were fresher and fitter than the Mexicans that is a big compliment to my players.
"Not only did they have belief but physically they prepared so well to play this match. That of course gives us enormous confidence going forward."
Van Gaal also admitted that he used the World Cup's first 'cooling break' to help his side pull off the comeback.