The Red Devils went into the clash with reigning Premier League champions Leicester City at Old Trafford on the back of three-straight defeats before producing their best performance of the season.
United won 4-1 course of a first-half flourish and it was all made possible by Mourinho's words prior to the match, as disclosed by centre-half Smalling.
"The boss really wanted to get the enjoyment factor across," said Smalling, who scored United's opening goal.
"He stressed how there is 70-odd thousand people in the stands who want to be in our shoes and in his shoes.
"It's a case of realising how lucky we are and how we should go out there and enjoy it.
"You can see that everyone did enjoy it and the message clearly did get across."