The result moves Forest three points above the Premier League dropzone.
Pereira said afterwards: "We started with a good level. But after 15-20 minutes, we started to lose a lot of possession, second balls and duels. We conceded a lot of set-pieces. We suffered until half-time.
"In the second half, I asked them to be themselves and play at our level. I asked them to play the same way we started the game and told them something will happen. And I am happy that they played with personality and organisation. It was an important win.
"I have a team that have the quality to play with the ball. But it's difficult to play in our way if you lose the ball often. Tottenham were very aggressive in the duels. It was not our intention to defend but they pushed us. We had some luck till half-time.
"But it was a good time to score the opener. We studied our opponents during the set-pieces and we scored. Set-pieces and even throw-ins are very important at the moment as in football, in every situation, we can get a goal.
"After the (Europa League game) in Denmark, it was important to rest. I tried to balance the energy. The players who played against Midtjylland and today showed that they have the quality to face the next games.
"For me, it's just three points. We got it. Next game, we have the chance to do it again. And we need to go there to get those points again. This will go on until the end of the season."