Belgium coach Roberto Martinez said his players were weighed down by a "fear of losing" in their shock World Cup defeat by Morocco on Sunday.
The world's second-ranked side will have to beat 2018 runners-up Croatia on Thursday to be sure of a last-16 place after their 2-0 loss at the Al Thumama Stadium.
"I do think it's because we played with a fear of losing," said Martinez.
"They work so hard for each other off the ball but then on the ball I don't see that enjoyment...
"We are a team that is usually playing on the attack. We're not playing with joy. It's maybe the weight on our shoulders."
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Belgium have reached at least the quarterfinals of the past four major tournaments and finished third in the 2018 World Cup.
They sit second in Group F, having laboured to a 1-0 win over Canada in their opener, ahead of Sunday's later match between the North Americans and Croatia.
"In the last game we have to play to win it and as if we have nothing to lose," added Martinez.
"If we win against Croatia we're (still) in the World Cup and that's a big motivation."
Captain Eden Hazard was a peripheral figure for long periods and was replaced by Dries Mertens with half an hour remaining.
"Eden, his role was to try and get to 60 minutes. We have to learn from the past," said Martinez.
"He had a very strong performance, probably the best I'd seen him since against Portugal in the Euros (last year)."
Injury-plagued Hazard scored the winner against Portugal but then was forced off late on with a hamstring injury that kept him out of Belgium's subsequent quarterfinal loss to Italy.
"We had to learn from the past. It was too much of a risk in that moment," added Martinez.
Veteran defender Jan Vertonghen said the defeat was down to a lack of creativity in attack.
The Belgians managed only four attempts at goal in the second half and their clearest opportunity fell to Michy Batshuayi in the fourth minute.
"We're hardly creating any chances. A lot of things go through my mind now, but those are things that are best not said on camera," Vertonghen told broadcaster TV Sporza.
"It can only get better. We wanted to qualify for the second round today against Morocco. It didn't work out.
"Now it's make or break against Croatia on Thursday."