What prayer does is change us to conform to God's will. The conclusion was that God out of His loving kindness allows us to participate in His will when we pray. (Example: Abraham's prayers regarding Lot Genesis 19:29; Jonah's prayers for Nineveh; Simon the shoemaker and all the Christians in the Mokattam miracle). We cannot logically say that Jonah or Abraham or Simon influenced God's mind as He is omniscient, instead these prayers allowed them (creatures) to participate with God (Creator) in accomplishing His sovereign will before the beginning of time.
It is sound to say that prayer helps us to accept God's will.