And the end of the end of the Amidah we say these words “May it be the will of G-d.”
Prayer is asking G-d to create HIS will. Asking G-d to make a new will to do something that was not in the plan and grant it to you any way.
This is the uniqueness of prayer.
I know until this point it was not you will, so I am asking you G-d to change your plan and make it your will in order to accommodate me.
This is what it means when we say that G-d listens to every prayer of every mouth that G-d is prepared to change HIS plan for the world. And this is in response to our prayer.
Whether it is for a prosperous year or healing of the sick ETC.