"It's normal that Barcelona think that January could be a bad month for us when they look at our fixture list," Mourinho said on Saturday.
"We have two derby matches (against Atletico Madrid in the quarter-final of the Kings Cup) and league matches against Villarreal and an improving Almeria side.
"If we get through (against Atletico in the cup) we will have Villarreal or Sevilla (in the semi-final). However, we have to be positive and take it one match at a time and look to win all the matches."
Madrid, two points behind Barcelona in the league, host third-placed Villarreal on Sunday at the Santiago Bernabeu and then entertain neighbours Atletico in the first leg of their Kings Cup quarter-final clash on Thursday.
In the league Real have bounced back from their 5-0 mauling by Barcelona at Camp Nou with four consecutive league wins and Mourinho realises his side can't afford to drop many points if they want to dethrone Barcelona.
"It is a league where teams don't drop many points," said the Portuguese. "Barcelona have dropped five and we have dropped seven. That doesn't happen in other leagues but it does here.
"However, the team with the most points, whether it be 100, 80 or 70, wins the league just like in other championships."
Portuguese international centre-back Pepe has joined striker Gonzalo Higuain on the sidelines after injuring his calf in training and is expected to be out for a month.
"He (Pepe) could have got injured at home or here in training," said Mourinho. "People getting injured is normal and these things happen."
The return of Brazilian international Kaka, after six months out with a knee injury, has been a major plus for Madrid and Mourinho confirmed the playmaker would play some part against Villarreal on Sunday.
"He (Kaka) has to play. If we are losing, drawing or having problems he has to come on because he is the only striker we have," explained the former Chelsea coach.
"If everything is going well and we are winning he will also play to get more minutes and give other players a rest. Kaka will play whether things are going well or badly."