The Spaniard, 23, has conceded 16 goals in 17 games for the English champions during the current campaign.
Despite United's shaky start in the Premier League, De Gea is satisfied with how he has been performing for the Red Devils.
"I'm very happy with [my form]," the shotstopper told the club's official website.
"I feel like this is a particularly good moment in my career right now and I hope to continue in the same vein. I feel like I'm always improving and I want to make sure that continues."
De Gea arrived at Old Trafford from Atletico Madrid in summer 2011.