The Seagulls stunned Jose Mourinho's side in their first home game of the new campaign, scoring all three goals in the first half with Glenn Murray, Shane Duffy and Pascal Gross all on the scoresheet.
However, Hughton refused to bask in the glory of the victory for long, instead quelling expectations and insisting that a difficult season awaits his side.
"It shifts the mood, but it doesn't change anything for this season. It's going to be a tough season. The three teams who came up are capable of taking points, and this division is as competitive as ever," he told Sky Sports News.
"If we think it's going to the same, or easier than last season, it's not going to be. We have to make sure our level of performance, if not at this level, needs to be somewhere near it, to get points. I thought the tempo right from the start, we always had an outlet. If you score three goals against any of the top six, it's always a good feat.
"I think within the group, they were that disappointed with the overall performance [at Watford], they were that keen to put on a show, and redress that balance. Sometimes you do that, things go your way, sometimes they don't. I think we forced things our way today with a very good performance.
"[Murray's performance] was excellent. On days like this you don't generally like to single out players. On the whole the team were excellent, you but you need someone to lead the line. Particularly later in the game, you need that outlet, and I thought he was very, very good for us today. I think we got confidence from a good start, and the first goal gave us a massive lift, and that carried us through the game."
Brighton are one of only 10 teams to have scored three goals in the first half of a Premier League game against United.