productivity hangover
noun phrase
A period after a burst of activity when one’s instinct is not to return to normal levels but to drop to near-zero in order to recover.
On slow days, Ismael could handle the low-but-steady flow of customers all day with no problem. But on days with a lunch rush, when things calmed down again around 2:00 he had a harsh productivity hangover and found it very difficult to deal with even the normal levels.