Goals from Chris Smalling and substitute Romelu Lukaku saw second-placed United see off Bournemouth on Wednesday following last week's shock defeat to relegation-bound West Brom at Old Trafford.
Saturday's 1-0 loss against lowly WBA handed neighbours Manchester City the title, having halted their trophy celebrations in the derby a week earlier.
Still disappointed with the defeat to West Brom, manager Mourinho lamented United's record against sides further down the table following losses to Newcastle United and Huddersfield Town, and draws against Stoke City and Southampton.
"I spoke with them about it," Mourinho said during his news conference, with United 13 points adrift of City, who could regain their 16-point lead against Swansea City on Sunday. "I think we are inconsistent, and we are inconsistent many times in our attitude.
"With our top five opponents, we didn't lose any points from them. Against City, we won, lost. Against Spurs, we won, we lost. Against Chelsea, we won, we lost. Against Liverpool, we won, we drew so we got one point from Liverpool. Against Arsenal, we won and we still have one match to play so we are not going to lose, so we didn't lose points in the two duels against direct opponents.
"But then we lost three points against teams that were promoted. We lost against Huddersfield Town, we lost against Newcastle United. We lost points against teams who are probably going to be relegated, or are in this group of the relegation fight. We lost three points against West Brom. We lost two points against all the other teams involved in that fight, Stoke, Southampton. So I think we were not consistent and you pay the price. You pay the price.
"Change has to be based on their attitude, their mentality. It's about that. This season of course was a much better season in the Premier League for us than the last one. The last one we finished sixth. I know that the Europa League was a target and you lose a little bit of focus. From a certain moment the Europa League was fundamental and we lost a few points in the Premier League but a much better season.
"We are quite safe in the top four. We have big chances to finish second. We already have more points than at the end of last season, with more goals, with less goals conceded, was much better. But could be even better. I don't say [we could] be champions. I don't say that because Manchester City are much better than us. The difference in points shows that. But we need to be more consistent in our approach."
Mourinho continued: "I know how to win titles, in case some of the new guys don't know, I won eight championships in four different countries and three in this country. I know why you win and I know why you don't win.
"No doubts about City's quality, no doubts in any circumstances they would win this title because they are the better team, but we could have, I would say, 10 more points than we have. No doubts. We should have 10 more points than we have."