After ending 2017 with a disappointing run of three successive draws, Mourinho's side have won all five of their games in the new year.
United, who are second in the Premier League, will now hope to carry that momentum into Wednesday's tricky contest against Tottenham at Wembley. Alexis Sanchez, whose signing last week has further buoyed the club, is poised to make his United league debut.
Mourinho told MUTV: "We have managed to win every match in January, I think three Premier League matches and two cup matches, so five victories makes a happy camp.
"We are playing with a good balance. It is not easy to not concede goals because of the high quality of football in this country but scoring goals and winning matches is very important because we need points. We are playing well and we deserved these results."
Spurs are eight points behind United and are facing a fight to get back into the top four but Mourinho has no doubts about the quality of Mauricio Pochettino's side, who were runners-up last season.
The Portuguese said: "Spurs are one of the top teams in the country - not a title contender because they are too far away, but I say honestly they are a Champions League contender. They can reach that level.
"They have some of the best players in the country, a very good manager and are a very difficult opponent.
"It is a really big game. The difference between us and Spurs is seven or eight points, but the reality is they are a top team in terms of their quality and ambitions, and a team of our level, so it is a big match."
Mourinho has close to a fully-fit squad - Zlatan Ibrahimovic and Eric Bailly are the only absentees - and is pleased they are fighting on despite trailing leaders Manchester City by 12 points.
Speaking at his pre-match press conference, the Portuguese said: "It's hard. Last season was hard, this season is hard. Last season we gave up that fight when we felt it was going to be very difficult to do it, plus the injuries, plus the Europa League. But this season everybody is there."
Mourinho is expecting a good occasion at Wembley, although its status as Spurs' home ground for the fixture will make for a different atmosphere than usual at the national stadium.
He said: "I was at Wembley for Tottenham versus Chelsea and I had that feeling that Wembley is Spurs' home, because it was full of their supporters. I am used to going to Wembley when it is 50-50 with supporters, so it was the first time I went like that. It is an amazing stadium and one for us to enjoy."
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