Manager Dave Edmondson says Bristol Academy paid the price for being too friendly in their 5-0 Champions League quarter-final loss to Frankfurt.
Edmondson also admitted progressing in Europe was "beyond his realms of optimism" with the return tie in Germany on Sunday.
"I saw one or two bits, laughing and joking with mates on the pitch. That is where we are a bit soft," he said.
"There is no such thing as a mate on the pitch."
The three-time Champions League winners and seven-time German Bundesliga champions delivered a harsh lesson to Bristol.
"Hopefully they will learn a lot from it and see that is what top international players can do," the 43-year-old continued.
|Bristol Academy's Champions League journey|
|9 October 2014||Round of 32 - first leg||4-0 win v Raheny|
|16 October 2014||Round of 32 - second leg||2-1 win v Raheny (6-1 on agg)|
|8 November 2014||Round of 16 - first leg||1-0 win v Barcelona|
|13 November 2014||Round of 16 - second leg||1-1 draw v Barcelona (2-1 on agg)|
|21 March 2015||Quarter-final - first leg||5-0 defeat v Frankfurt|
"For the first 10 or 15 minutes, all that Frankfurt did was earn the right to play, which is something we have to learn some time.
"Yes, you have a way that you want to play - you want to be pretty and do the right thing - but you have to earn that right to start with.
"Whether you are 1-0 down, it's 0-0 or you are 5-0 down with a minute to go, you have to earn the right to play."
The heavy defeat in Europe's top club competition came 128 days after Bristol progressed to the last eight with a remarkable 2-1 aggregate win over Barcelona.
It also marked the start of the 2015 season for Bristol Academy, who face another knockout fixture on Tuesday when they travel to Everton in the fifth round of the Women's FA Cup.
"We have to forget this really and concentrate on Tuesday," Edmondson added.
Victory against the Toffees will set up a home quarter-final meeting with third-tier side Charlton Athletic on Sunday, 12 April