The gemara in Brachos says that one must stand the distance of two door ways away from the entrance of the Shul during davening. The Lechem Avirim (Al Hatorah Parshas Balak) explains this B'Derech Drush.
To stand in front of the King of all Kings and make our simple requests is quite frightful. After all have we respected all his wishes? How dare we stand before him with more requests? However Chazal tell us "Pischu Li... KiChudoi Shel Machat VaAni Eftach Lachem Pesach Shel Ulam", Hashem asks us to open up in our hearts a small opening no bigger than the tip of a needle and then He will reciprocate and open up a huge gate through which He will send us His blessing.
This, says the Lechem Avirim, are the two doors of Tefila. One is the small door we make in our heart and the other is Hashem's gigantic door. When nervous about davening to Hashem we should keep this two door arrangement in mind. Then we will be less frightful, knowing that Hashem does not expect us to match his largesse.