The Spain international had a shaky start to his career at Old Trafford having arrived from Atletico Madrid for £17.8million in the summer of 2011.
The 22-year-old has since established himself as first choice for the Red Devils but he is still not taking anything for granted.
"It's more about all the things you learn rather than one individual thing," he told manutd.com.
"It's an ongoing process as well, especially when you come to a club from another country. The whole thing is a great experience.
"At first, everything is new. The football, the culture and how people live...it's about learning how things work at the club and getting to know your team-mates.
"The whole package has been a lesson for me. The support I have had from everyone at the club has been fantastic.
"First of all you have to have the belief in yourself and self-confidence, but that is enhanced once your team-mates and people within the club show their confidence in you and their support.
"It's a top dressing room and a great one to join.
"Everyone in the squad helps you a lot and the settling-in process is made a lot easier by the fact that there is such a warm atmosphere here."
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- Atletico Madrid