Manchester United are battling against a lack of confidence, according to Chris Smalling.
The defender said "heads dipped" after a host of missed chances against Young Boys before Marouane Fellaini snatched a late winner to send United into the round of 16 of the Champions League on Tuesday.
"We created some good chances, not just half chances, and I think heads can dip when a few of those don't go in," Smalling said.
"You could see the relief in our faces knowing that we had qualified and not have to go to Valencia and really make it hard for ourselves."
After securing qualification from Group H with a game to spare, United will now turn their attention to improving their position in the Premier League table, starting with Saturday's trip to Southampton.
Jose Mourinho's team are seventh, 14 points behind leaders Manchester City and seven adrift of the top four.
"We had two targets speaking before that Palace game: getting back into that top four and qualifying," Smalling said.
"We've qualified now and now it's all about our league form."
Despite booking their place in the knockout rounds, Paul Scholes was far from impressed with United's performance against Young Boys, branding it "awful."
Mourinho refused to address the criticism after the game but match-winner Fellaini admitted that after five wins from their last 13 games they have to take it on the chin.
"Criticism is part of football but we have to work," said the Belgian, who scored his second goal of the season against the Swiss champions.
"We are a team, we are together, and give everything too. Together we have to move forward and take the points.
"I think the mood is good. The players are happy but the most important thing now is to focus on Saturday and three points."