The 22-year-old has nailed down the No.1 shirt at Old Trafford in recent months after sharing the role with Anders Lindegaard.
De Gea has endured some difficult times in England, but the former Atletico Madrid man believes his experiences have improved him as a player.
"I've changed a lot in Manchester. I've spent two years in their football culture and it makes you change," De Gea is quoted as saying in the Daily Star.
"I'm more mature as a person and a player. I'm a very different person from when I arrived in England."
De Gea has been rewarded for his fine form with a call-up to the Spain squad for the upcoming World Cup qualifiers against Finland and France
The keeper, who has yet to win a cap for Spain, has been drafted into the squad as cover for the injured Iker Casillas and he is keen to take his chance to impress coach Vicente Del Bosque.
"This is a special moment for me and a big step in my career," added De Gea.
"I want to enjoy this and learn from my team-mates, who are my and many other people's idols.
"It's a pity Iker Casillas is out. We all know he is our captain and a legend but I'm happy to be here, even if it's because of his injury."