Two goals in the final seven minutes gave the Hornets a thrilling 3-1 Premier League win over United at Vicarage Road on Sunday, condemning the visitors to their third consecutive defeat in all competitions.
Mourinho has been affected by a spell that has seen them lose to rivals Manchester City, Feyenoord and Watford and acknowledges the latest loss will have an impact on his players.
But the former Chelsea boss stressed the importance of seeing the bigger picture and called for positivity from his squad to turn the situation around.
“I’m sad – obviously I’m sad,” Mourinho told MUTV.
“I’m always concerned when we don’t get the result we want. “But as I was telling the players, there is only one way – tomorrow we have a training session 10:30 in the morning. We have to be there and we have to work, but they have to show themselves a certain attitude towards the negative moments.
“I gave them as an example Ashley Young, who was phenomenal in his attitude and determination.
“We need positive people to give us positive feelings because obviously the next time these guys are going on to a football pitch they are – as a normal human being – going to obviously feel the weight of the defeat.”
Mourinho felt United did not deserve to lose the game, with Watford’s two late goals coming at a time he felt most satisfied with his team’s performance.
He continued: “I have this capacity of balance. Nobody saw me running around the pitch because we were winning a couple of matches and nobody sees me now really depressed.
“We had a strong period where we showed intensity, quality and desire. There was a creation of opportunities – the goal, the almost goal [Ibrahimovic’s header] when it was a great save by the opponent.
“The game was going really well. The pressure was there and the team was trying to win, showing confidence.
“But, in one completely isolated counter-attack – I don’t remember David de Gea touching the ball in the second half – they scored a goal.”
Mourinho has now lost three competitive matches in succession during the same season for the first time since he was in charge of Porto back in the 2001-02 campaign.
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