The Blues have led or shared the lead since the opening round of fixtures and entered this weekend's matches seven points clear with eight matches remaining, beginning at QPR on Sunday.
"To be top of the league since day one shows consistency, stability, confidence and a brave approach to every game," Mourinho said.
"We are there, we deserve to be there, but every game is difficult
And we still have eight matches to play."
Mourinho knows the Premier League - a championship more competitive than Italy's Serie A or Spain's Primera Division, in his opinion - can throw up twists and turns in the closing weeks.
The Blues boss was not surprised to see holders Manchester City slip up at Crystal Palace last Monday to all but end their title hopes.
Mourinho added: "This is the Premier League
In other competitions it's difficult to believe that the top team can lose four, five, six, seven matches.
"In almost every country it's very difficult for a top team to lose so many matches.
"Here, yes
It's possible
I'm not surprised
It's happening to everybody
Everybody loses matches, everybody loses points."
Mourinho will hope Chelsea are not among them at Loftus Road.
Source : PA
Source: PA