הלכה על ברכות 67:5

Shemoneh Esrei, the weekday Amida, is divided into three parts: praise, petition, and thanksgiving. While reciting the first three berakhot, we resemble slaves who offer words of praise before their master. While reciting the middle blessings we are like slaves who make requests of their master. When we recite the last three blessings, we are like slaves who gracefully accept reward from their master, then are dismissed and go on their way (Berakhot 34a).