A wise person once remarked that Megillat-Esther is read right after a fast, at that time we're still hungry and tired. A few months later we read Megillat Eichah (Lamentations) and at that time we're usually full, as we're getting ready for the long night-day fast of Tisha b'Av. There is a lesson here: we come to the Megillah of Lamentation full and confident – and then we read about a tragedy. To the Megillah of Esther we come hungry and thirsty – and then we read about great joy and salvation.