I decided to do my sketch on the Greek myth of Alcyone and her husband Ceyx. Alcyone and Ceyx called each other "Zeus" and "Hera", which angered Zeus, so when Ceyx went off to sea, Zeus threw a lightning bolt at his ship. Morpheus, the god of dreams, appeared to Alcyone as an apparition of Ceyx, telling her of his demise. Alycone was so wrought with grief that she threw herself into the sea. The gods took pity on her and turned both her and Ceyx into "halcyon" birds, or kingfishers (although in this culture the Halcyon bird is a mythical kingfisher which lays its eggs in a hovering nest over the ocean).
I chose this because I stumbled upon this myth and really liked it, and the Herbert James Draper piece based on it, which you can see here. I figured this could work for both worst day (she finds out her husband is dead) and best day (she and her husband are saved and immortalized as birds).