Euro 2012 - Pearce: England were naive, lacked belief
But Robben scored a stoppage-time winner as England were punished for losing concentration in the dying seconds.
"We probably showed a little bit of naivety and a slight lack of belief,' Pearce told ITV. "That's something we've got to get into the squad, going forward.
"Once we'd got ourselves back into the game, we're disappointed to have been beaten. But there were a few good showings, we learned a lot and that was the exercise."
Pearce is expected to be replaced by Harry Redknapp before England play at Euro 2012, but he said he would be delighted to continue in his role.
"I've offered my services in the summer," he said.
"I've really enjoyed the last few days, it's been fantastic and the players have been outstanding. Their focus and contribution in training has been very good. I enjoyed tonight."
Speaking about his decision to appoint Scott Parker captain ahead of Steven Gerrard, Pearce said: "I feel as though he's got the personality around the other players and I think he would grow being the captain.
"I think the other players respect him and I think he's a very unselfish man. Make no mistake - there were a lot of candidates to do the job but I felt Scott was the right man for the job tonight.
"I spoke to Steve quite a bit about international football and various other things but he's quite understanding. He quite understands that it's all part of the game."