The question is sometimes asked: If God’s will and purpose are unalterable, why pray? The answer is simply: Because the divine purpose, which any answer to prayer must represent, includes the prayer itself. It is enough that He “who worketh all things after the counsel of His own will” (Eph. 1:11) invites and exhorts His people to “come boldly unto the throne of grace” to “let [their] requests be made known unto God” (Heb. 4:16; Phil. 4:6).
But prayer is not merely petition, as many suppose. It is one aspect of active communion with God (meditation on the Word being the other) and includes adoration, thanksgiving and confession, as well as supplication.
An example of this in the passage of our Lord’s prayer in the garden when He laid aside His glory, became “a servant” (Phil. 2:7) and “learned obedience” (Heb. 5:8; Phil. 2:8). In this place of subjection He made definite and earnest requests of His Father, but closed His prayer with the words: “Nevertheless, not My will, but Thine, be done” (Luke 22:42) with the result that He was “strengthened” for the ordeal He had to face (Luke 22:43).
Thus prayer is not merely a means of “getting things from God” but a God-appointed means of fellowship with Him, and all acceptable prayer will include the supplication — as sincerely desired as the rest: “Nevertheless, not My will, but Thine, be done.” source