I remember reading a myth as a child, but have not been able to find it again ever since.
It starts like a typical Apollo myth: Apollo has a young best friend/lover, and they are inseparable. Then the young man's sixteenth birthday approaches (or was it some other day symbolizing the coming of age?), and Apollo wants to give him the best present a mortal has ever had. But he is neither powerful enough to grant the best, nor wise enough to know what the best is.
Apollo then goes to Zeus and asks him to give his friend the best present on his special day. Zeus agrees and Apollo tells his friend, both awaiting the day with happy apprehension. But then, on the birthday, the young boy is struck by lightning.
Apollo is very angry and demands an explanation of Zeus. The explanation: Zeus killed the boy on the happiest day of his life, before he had met the sorrow of the drudging adult routine. This was the best present a mortal could have. Apollo understands this and mourns his friend.
I have forgotten the name of the boy. Upon checking, it's not one of the usual suspects (Hyacinth, Cyparis). I also don't know any more where I have read it, although it's not in the thick Kuhn edition of the Greek myths in my parents' home.
Does anybody recognize the myth? Can you give me more info about the name of the boy, and a source where it is recorded?