Chris Coleman said Wales may have been guilty of complacency after qualifying for Euro 2016 - but insists that will not undermine their preparations.
Sunday's 3-0 loss to Sweden means Wales have won only once in seven matches.
However, their manager is confident they will be ready for their Euro 2016 opener against Slovakia on 11 June.
"We get a bit of success, a bit of expectation, sometimes a little bit of complacency and that can give you a little slap in the face," he said.
"Maybe that's what's happened to us, certainly today."
Wales flew out to their French training base in Dinard after the game. They face Slovakia, England and Russia in Group B at Euro 2016.
Coleman believes his side are the "underdogs" but added: "It doesn't mean we can't produce something special, because we're capable of it."
|Wales' Euro 2016 Group B games|
|Fixture||Venue||Date & time||BBC coverage|
|v Slovakia||Bordeaux||11 June, 17:00 BST||BBC TV, BBC Radio 5 live|
|v England||Lens||16 June, 14:00||BBC TV, BBC Radio 5 live|
|v Russia||Toulouse||20 June, 20:00||ITV, BBC Radio 5 live|
|Live text commentary on every game on BBC Sport website|
Wales were 'naïve'
A Wales side without Joe Allen, Joe Ledley and Hal Robson-Kanu - and with the pivotal Gareth Bale making only a second-half substitute appearance - were soundly beaten in Stockholm.
"We were a little bit naive, which would be my criticism today," said Coleman. "Normally we do a lot to work on being a bit more streetwise on the pitch, like Sweden were.
"We saw how many times they fouled us on the counter-attack to break it up. There's nothing wrong with that - that's international football.
"I'd rather that today than me sitting here next week complaining about the same problem."
'A huge week in front of us'
Despite the manner of the defeat, Coleman refused to be downbeat as Wales embark on their first major tournament since the 1958 World Cup.
"The boys are disappointed because they know they can play a bit better than they did in certain areas," he added.
"In saying that, we've got a huge week in front of us - and I'm very positive.
"We know what's coming, we know it's going to be a huge test and this is not the time for us to pull apart this particular performance.
"It's the time for us to remember what we've done over the past two years and remember our strengths and our qualities.
"When we're 100% at it and we mean it, then we're a good team. We'll pick the boys up."
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