Manchester United boss Erik ten Hag said a lack of self belief is the reason for his side's poor display against Brighton.
The Red Devils struggled to assert themselves against the Albion at home on Sunday in the Premier League.
United lost the game 2-1, having trailed 2-0 at half-time to two Pascal Gross goals.
"I think it was a good start and then after we dropped down a level in belief and we made mistakes and the opponent punished us," Ten Hag said in a news conference after the game.
"I can understand that [a lack of belief] after last year but it's not necessary.
"They are good players; self belief is from yourself.
"I know it could happen, but I think we should have done better, that's clear, but also it will not come overnight.
"Today we had a worse period during the first half and we have to learn from that. That's also clear."