The Sefer Kav HaYosher says the following: Taanis Esther is a day that is very auspicious for one's prayers to be answered in the merit of Mordechai and Esther. Whoever needs mercy for any particular need should put aside time for themselves and do the following: First, recite Chapter 22 in Tehilim. Then, pour out your heart to Hashem and ask for all your needs and mention the merit of Mordechai and Esther (whose merits saved us from Haman). The Gates of Mercy will be opened and your prayers will be accepted beratzon .