what is the significance of this quote? "In the morning, in the evening, Aint we got fun."

The song "Ain't We Got Fun" is significant for a number of reasons. The opening lyrics ("In the morning/ In the evening/ Ain't we got fun") imply a carefree spontaneity that stands in stark contrast to the tightly-controlled quality of the lovers' reunion. This contrast is further sharpened by the words of the next verse, which run: "Got no money/ But oh, honey/ Ain't we got fun!" It is bitterly ironic that Gatsby and Daisy should reunite to the strains of this song, given the fact that she rejected him because of his poverty.