The Spaniard has come through a testing first six months in English football which saw him begin the season in the team before having a reduced role as a substitute.
That led to suggestions manager Louis van Gaal did not rate the Â£29million summer signing from Athletic Bilbao
However, the 25-year-old has now started the last eight matches and scored twice in Saturday's 3-1 win over Aston Villa.
"I'm very happy
Even when I was not playing, I was also happy
I am at Manchester United
I feel really lucky to be here," he told United Review.
"It's my dream to be here for a long time because I am in the right team, in the right league and in the right country
I want to stay at the club for many years to come.
"I feel I quickly adapted to this league and this country because I am so comfortable here.
"I think (we at) Manchester United are always helping each other to adapt and to feel like we're at home.
"I feel really good at United and I hope to stay here for a long time.
"The manager has to decide who is playing or not but we have to respect always the decision he makes
The manager wants the best for the team, the best for us and we have to follow him always."
Source : PA