הלכה על יומא 106:3

Upon the conclusion of the prayers of supplication, one recites Yihyu le-ratzon again and takes three steps backward, thereby departing the King’s presence. The Sages say that if one prays and does not depart from the Amida properly by taking three steps back and saying “Oseh shalom…,” it would have been better not to have prayed at all (Yoma 53b). One who does not take leave properly demonstrates that she does not understand that she was standing before the Almighty King, and she thus demeans prayer.