Ruben Amorim has admitted his Man United side buckled under the pressure against Bournemouth on Sunday afternoon.
The Red Devils sought consecutive wins in the Premier League after a 2-1 disposal of rivals Man City in the derby last week, but were handed a humiliating defeat at Old Trafford.
Goals from Dean Huijsen, Justin Kluivert and Antoine Semenyo capped off a convincing 3-0 win for Bournemouth.
Amorim hinted that the worst is still yet to come, as he argued that his side will 'have to suffer again', speaking after the game.
'This game was hard on us. We suffered again on set-pieces and we were a bit nervous, I felt it in the stadium,' he told Sky Sports.
'The penalty and another goal are really hard here. We tried to score some goals but it was a tough match so let's move on.
'If you look at the game, we were not conceding anything before the first goal, we had opportunities. If we manage to score the first goal then the game should be different. We want to score but we are too nervous. We have to fight this.
'After the penalty, we need to control the game better because we know this situation is really hard. We have to control better this moment.
'We have to focus on the job and not what you feel in the stadium. It's the only way I know how to focus my players.
'We have to suffer again but we will try to win. We will do it until the end.'
United conceded three goals at home in the Premier League for the fourth time this season after Sunday's defeat.
Amorim's men lie 13th place in the table, nine points off Nottingham Forest in fourth, who occupy the final Champions League qualification spot.
They travel to relegation strugglers Wolves on Boxing Day, hoping to turn around their tumultuous form.