What does churchill mean when he says, "all fall back into the past- not only distant but prosaic?"

June 4, 1940

House of Commons

The position of the B. E.F had now become critical As a result of a most skillfully conducted retreat and German errors, the bulk of the British Forces reached the Dunkirk bridgehead. The peril facing the British nation was now suddenly and universally perceived. On May 26, “Operation Dynamo “–the evacuation from Dunkirk began. The seas remained absolutely calm. The Royal Air Force–bitterly maligned at the time by the Army–fought vehemently to deny the enemy the total air supremacy which would have wrecked the operation. At the outset, it was hoped that 45,000 men might be evacuated; in the event, over 338,000 Allied troops reached England, including 26,000 French soldiers. On June 4, Churchill reported to the House of Commons, seeking to check the mood of national euphoria and relief at the unexpected deliverance, and to make a clear appeal to the United States.

in what passage i'm sorry but i don't see anything there.