United travel to Anfield on Sunday with just a two-point lead over their arch rivals in the race for fourth place in the Premier League.
And, having seen his team have Chris Smalling sent off in the Manchester derby against City and Angel Di Maria dismissed in the FA Cup quarter-final loss to Arsenal this season, Van Gaal is keen for his team to keep their emotions in check.
"I have been the referee in the game that we do on the training pitch," Van Gaal said.
"I have whistled in a way that they have to control their aggression for example - to prepare for them for the atmosphere.
"I mentioned that [in training], control of emotions is also a challenge."
United face Liverpool on the back of one their best performances of the season in last weekend's 3-0 beating of top-four rivals Tottenham.
But Van Gaal was keen to stress that the victory over Spurs will count for little if United lose at Anfield.
"I think every win is better than losing or a draw," he added. "We played very good in the first half [against Tottenham].
"It was also good to have an evaluation that was positive. It's also good for the players.
"But it says nothing if you lose the next match. The next match is against Liverpool and it's a ground Manchester United has won not a lot at."
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