The Dutchman admits it was tense game against the Seagulls on Sunday.
"It was a good game," said Maatsen to the club's website. "There was a lot of tension at the end, but we worked hard and stuck together as a team. We're very happy to get these three points at home, so it will give us a good spirit for the next game.
"We showed we can fight. There was a lot of tension at the beginning as well, but these are good challenges. At the end there was a little bit of tension from the fans, the long added time to play, the VAR, all this stuff, but I think it's good for us.
"We have the three points now and we're really happy. We will take this boost to Manchester United for the next game."
On Conor Gallagher's red card before halftime, Maatsen also stated: "Sometimes it is the passion, but we all know we can do better or make other decisions. Yesterday that happened, we move on and we know what we have to do with each other. We will just keep working and it will be all right.
"I think in every game you have to fight. The team really wants to fight for each other and you saw that against Brighton. On the pitch there were some good tackles, the intensity was high. We try to do that in every game."