Mourinho felt the word solid could be applied to his side in a collective senseon a day when Zlatan Ibrahimovic's 28th goal of the season preceded efforts from the impressive Henrikh Mkhitarayan and Marcus Rashford, who scored his first league goal since September after stepping off the bench.
United extended their unbeaten record to 21 league games and climbed to fifth place in the table, four points below fourth-place Manchester City, who have played a game more.
"We have to keep focused, keep working, keep believing that we can reach the top four".
"I'm not anxious, I just play my game, enjoy it, and it seems like the older I get the more intelligent I get".
"Yes. I was expecting that because I knew the reasons why he was coming", Mourinho told reporters in December.
Everton has now won seven consecutive Premier League home games, all of which Lukaku has scored in.
"I feel like Benjamin Button - I was born old and I will die young". "When you play a team that is sad, if you score first the game is nearly over because it is hard for them to react".
After struggling initially, Sunderland began to get a foothold in the game around the 20-minute mark, with Bryan Oviedo sending a free kick straight at Sergio Romero, and Lee Cattermole doing the same with a hit from open play a few minutes later.
Jose Mourinho appeared less than impressed with Manchester United's travelling support and their confusing choice of songs during the win over Sunderland.
"We keep going. We have another home game next Saturday (against West Ham United) and we have to try and win it".
The Uruguayan arrived in Manchester from Independiente amid much hype and expectation, but ultimately failed to deliver during his time at Old Trafford, scoring just 17 goals in almost 100 games before leaving for Villarreal.
Manchester United will take on Anderlecht in the first leg of their Europa League quarter-final tie on Thursday night.
"He was very good, " Mourinho said.
United still have the added of advantage of being in the Europa League, with that giving them another chance to qualify for the Champions League next season, so there is plenty to play for between now and May for the Premier League giants. Things today didn't go for us.