Vatosef Esther vat'daber lifnei Hamelech vatipol lifnei raglav vateivk vatischanen lo. (8:3)
The gemara says that the word Hamelech in the megilla is referring to Hashem.
Hashem says about the Baal Gaava - a haughty person, "I and he cannot coexist in one place."
Kol haholech b'komah zekufa k'illui docheik raglei Hashechina - Whomever walks with an erect posture (i.e. an arrogant manner) it is as if he is pushing away Hashem's 'feet'.
If Esther wanted to be in Hashem's Presence and daven to Him properly, she had to achieve the trait of humility.
She totally negated herself before Hashem! Not only did she not 'walk erect' (komah zekufa), she fell before Hashem's 'feet' (and thereby brought close the "raglei Hashchinah")!