Jimmy Smith's 20th-minute goal was enough for Orient to overcome a subdued Canaries side.
"We didn't deserve anything out of the game," said Lambert. "We have set ourselves high standards this season and we didn't match them.
"If anything I thought we had too much of the ball, which can be a problem at times, and we didn't know what to do with it.
"We seemed to be trying to score the perfect goal. They played really well and deserved to go through.
"It's always disappointing to lose a game but I can see the bigger picture and the big thing for us is the league, so we move on."
Source: PA
Source: PA