The 26-year-old former Crystal Palace player is looking forward to making his top-flight debut and is confident Hammers will hold their own against England's best during 2005/06.
"The celebrations after the promotion were just incredible," he said. "For all the players it was tremendous to be involved in something so special.
"But that's all gone now. This is a new season coming up and we've achieved nothing yet in this campaign.
"Now it's all about working hard and preparing to take on the Premier League. There is a feeling around the Club now, from the players and staff to the fans, that we're back where we belong.
"But we've got to prove it with our performances.
"Our preparation during pre-season is going to be extremely important. The manager will have his own ideas on how to best prepare the squad and what we need to work on.
"But from a players point of view, we just have to make sure that we're fit and ready to go right from that first whistle against Blackburn Rovers on August 13th.
Hayden has been impressed with the recent additions Alan Pardew has made to a squad, which Mullins believes was already close to Premiership quality.
And the former England Under-21 star welcomes the added competition for places.
"The Premiership is a tough League and you need top quality players," he explained. "The squad that won promotion was definitely strong, but the players knew that there would be additions over the summer.
"The manager warned as much and as a player you expect that, because when a Club wins promotion you have to strengthen.
"I've been impressed with the new players that have come in and hopefully they'll have a positive impact on the squad.
"It means added competition for places, but it certainly keeps you sharp and it's all good for the long-term future of the squad."
Having seen his old club Crystal Palace win Premier League status through the Play-offs only to drop straight back down, Hayden knows just how tough it is for promoted sides to survive in the top-flight.
But the Berkshire-born player is quietly confident that Hammers will cause a few waves amongst England's elite.
"I think we'll surprise a few people in the Premiership," he warned. "Of course, the step up is huge and we're going to have to raise our game accordingly.
"But I believe we can do it. We showed time and again last season that we could play against top sides, be it in the League or against Premiership sides in the Cup.
"This team has the ability to compete at the highest level and I don't think we'll struggle as much as some people might think."