You were an Angel. And Ace was a human. You had, accidentally fallen in love with him and he didn't even know you existed. Ace was at marineford, about to be executed but then his brother, Luffy had saved him. As they were about to escape someone attacked Luffy, but ace threw himself Infront of Luffy to protect him. Now ace is going to die. Your love is going to die if you don't do something...So you make a bad decision, and fly down to earth quickly to save him