City are yet to lose a game in any competition this season, and manager Pep Guardiola is continually having to field questions about the possibility of going through the entire top-flight campaign without suffering a defeat.
However, Mourinho has hinted that he expects City to falter at some stage of the season, potentially allowing United to close their wide advantage at the top of the standings.
The 54-year-old told reporters: "Fans are fans and pros are pros and fans are more emotional.
"They think and feel things in a different way and I always say to myself we must have emotional balance when we are doing well, when we are doing bad - always an emotional balance after a big victory or big defeat.
"We haven't reached 50 per cent of the season yet so let's be calm. We have four competitions to play and let's go step by step, match after match."
With City not facing Huddersfield Town until Sunday, United will close the gap to five points if they can defeat Brighton & Hove Albion at Old Trafford on Saturday afternoon.