Mourinho slated Pereira for opting to join Valencia rather than stay and fight for a place in his first-team.
The midfielder spent last season on loan at La Liga side Granada and has now returned to Spain for another campaign.
Mourinho wasn't impressed, but Pereira isn't fussed.
"It was difficult because they wanted me to stay in Manchester," he told Marca.
"But for me individually and for the options to play it was better to be here. Because it was better to come to Valencia to play games and help, because Manchester had little chance."
When quizzed on Mourinho's reaction, he said: "It did not hurt. I talked to him before coming here.
"On the one hand I'm happy because he loves me and I think that if I'm not a good player, I would not have wanted to stay. So I think on the bright side.
"If I thought negative it might hurt, but for me it's a good thing.
"I talked to him before coming here and I want to work hard and stay all year. I'm focused here.
"I want to be here and help the team all year, but I do not know what United wants in the future.
"I want to contribute the best and do the best all year in Valencia."
Pereira has made five appearances for United.
