Cristiano Ronaldo rattled in his sixth hat-trick of the season as Real stormed back to win at the Bernabeu in some style, capitalising on second-placed Barcelona's surprise 3-2 defeat at Osasuna on Saturday.
Mourinho's side continued to set a relentless pace, reaching 58 points from 22 matches and Ronaldo's 27th goal of the campaign pushed the team's tally to 75.
"There are still a lot of points in play, many games, and each one is difficult to win," Mourinho, who has won league titles in Portugal, England and Italy, said on Sunday.
"They will get harder to win because from now on teams are fighting to avoid relegation and for the European places.
"While it isn't mathematically resolved we have to keep winning. If I'm not wrong we need 39 points, 13 victories, to be champions. Obviously 10 points gives us a margin of error, but every game is tough.
"We will slip up, like we did against Levante in the first part of the season, but we have room for manoeuvre."
Real have only dropped eight points in the season to date, with defeats away to Levante and at home to Barca, and one draw at Racing Santander, and are on course to smash league records if they maintain their rhythm.
Mourinho's attempts to play down the euphoria fell on deaf ears in the local media.
"Madrid are so close to the title that it is difficult to see any other verdict in La Liga," sports daily Marca wrote on Monday.
El Mundo said: "Cristiano kills La Liga." El Pais wrote: "La Liga is theirs [Real's] and no one else's. This isn't a championship of two. Madrid know that, and of late Barca do as well."
Barca's faltering form, in particular on the road, their injury problems and accumulated weariness makes it hard to see them coming back to win a fourth consecutive league title.
They have already lifted three trophies this season, have booked their place in the May's King's Cup final and will return to Champions League action next week.
"There are still many points to play for but the sensation is that Madrid aren't going to drop very many," said sports daily As. "And Barca don't have the DNA of a pursuer."
