Manchester United beat Everton 2-1 at Old Trafford on Sunday, thanks to a Paul Pogba penalty-rebound and an Anthony Martial stunner.
The victory now means that the Red Devils are eighth in the Premier League table, having moved above Marco Silva's team. However, the game was not plain sailing as Chris Smalling's unnecessary foul in the penalty area gave Everton a lifeline, following a penalty of their own, going into the final ten minutes.
Speaking about United's recent performances to ESPN after the game, Mourinho said: "We are playing OK. We are not as rock solid as I would like, we don't have that killer instinct I would like.
"Some teams they have three chances and score three goals. Some teams without the ball, can resist and keep a clean sheet all the time.
"But for us in this moment it is is almost impossible to keep a clean sheet even with the phenomenal goalkeeper we have. And to score goals is really difficult for us - you can see that in this moment.
However, one player who is certainly firing for the Red Devils is Martial, who seems out to prove a point having been left on the bench for most of the season thus far.
On the Frenchman's performance, Mourinho said: "He took quite a long time to understand what we want, quite a long time for his brain and body to be ready for how we want him to play.
"At the moment he is playing very well. Even if he doesn't score, to create what he is creating, it is a solid performance for the team.
"He is understanding things he did not before. He wants to play and he knows that to do that he has to go in a certain direction. His performance without the goal would be a good performance.
"You cannot score every time you play, where you don't assist but you have a certain balance. That is the way I think it is going now."
It was Martial run that resulted in Manchester United's penalty in the first half. Paul Pogba stepped up to take the penalty with his unorthodox run-up and was fortunate to score from the rebound after Jordan Pickford had saved the original spot-kick.
Asked to comment on Pogba's run-up, Mourinho stated: "The thing I like is the desire to take it. I like the player that wants to take it. Paul, can he improve? I think he can.
"The goalkeepers know his running, they don't move and they are waiting for his decision so he has to learn from that but for me the most important thing is he wants to go again."
Following Manchester United's 2-1 triumph over Everton is a trip to Bournemouth, who have been the Premier League's surprise package so far this season. Mourinho will be hoping to make it three wins from four in the league and signify a return to form for the Red Devils.