Panel 1: We find ourselves at the clinic today. As John reads a patient's file, Jean looks out the window and says "Good morning, Doc! Isn't it a wonderful day today?"
Panel 2: Invoking the spectacular looking flowers that he probably should have noticed growing in front of the post office doesn't seem to get his get up and go going so we're looking at a mid-life crisis kind of thing.
Panel 3: Since everything she says tends to be answered by a trite almost-joke, Jean should know better than to ask what could be wrong with a day where the air is fresh and the birds are singing.
Panel 4: Since she's genre-blind, she's confused when Gloomy John is gloomy and tells her that what's wrong with it is that it's Monday.
Summary: This, I think, goes beyond the sort of smug ignorance that had Elly get all arch and superior about the messed-up priority of maintaining a sewage system when arts need funding more which blinds Lynn to the idea that people can find dentistry a challenge that one loves. There is also the fact that she's kind of lazy and can't understand creative types looking forward to working either.