Eriksen felt United started the match strongly and surprised Brighton, but after conceding the opening goal to Danny Welbeck, momentum swung in the visitors’ favor.
“I think we lost a bit of the momentum,” Eriksen said. “I thought we had it back with a goal just before half-time. But then we didn’t have the little luck or the clinical part to get back.”
The Danish playmaker highlighted Marcus Rashford hitting the woodwork and new signing Rasmus Hojlund having a goal ruled out by VAR as opportunities United failed to capitalize on.
With the score at 1-0, Pascal Gross and Joao Pedro extended Brighton’s lead before Hannibal Mejbri scored a consolation for United.
Eriksen believes United created enough chances to get back into the game but simply lacked the decisive finishing required.
“You have to (fight), already before that I think we were trying to come back and we were trying to be offensively (dangerous),” he said.
“I feel like we had enough chances to come back but we just didn’t take them. It’s been like this, the season so far. I think if we change that, I think a lot of the games will be a lot easier to play.”
The defeat leaves United with just one win from their opening five Premier League matches. Eriksen knows a tough test awaits in the Champions League opener away to Bayern Munich on Wednesday.