The daffodil usually stand for beauty in general (desire, art, grace, etc.), and the death of youth in particular.
It is also a symbol of deep regard.
There is a tale from Ancient Greece of a man named Narcissus who loved to look at himself; one day when he was looking at himself in a pool of water, he fell in and drowned. From his grave, a flower grew and this was the Narcissus (a less common name for the Daffodil).