Mata has earned hero status at Old Trafford after joining from Premier League rivals Chelsea in 2014.
But this season has been tough for Spaniard, and he has admitted that their current woes also makes it difficult for his family.
He told The Times: “People say, 'you cannot complain, you play football, pressure is for the people trying to make a living'. Of course, I understand that. But results dictate my life, my mood, my weeks, my relationships.
"It's difficult for my girlfriend. I'm sorry to her. And for my family. I don't speak because I'm angry."