I think Msgr Paul Glenn puts it aptly. This is an excerpt from his book entitled " Apologetics" published in 1931.
Q: “Well, if God is immutable,He is utterly changeless how can my prayers make any difference? If God’s decrees are all from eternity how can they be affected by prayers offered in time?”
A; God’s eternal decrees need not be affected. God has prepared from an eternity,an answer to EVERY prayer that can be possibly be made; and such answer is part of his eternal decrees. Of course the prayer must be offered, else the prepared answer cannot be given. Hence, the necessity of the prayer…
… Still, we need not go to Scripture for a proof of the point in question. Reason makes the matter clear. God, the all perferct Father of Men, has implanted in the hearts of His children a longing for his gifts and a tendency to ask for them; and this would be futile on the part of God if prayer could not be effectively offered: and God performs no futilities, for He is all wise. Thus our prayers DO make a difference, a great difference, and ALL THE DIFFERENCE. The ETERNAL answer is waiting in every petition - but the petition MUST be made. The boundless gifts of God await the offering of diligent prayer ---- and ONLY the diligent prayer must be offered. There is no prayer that a man can offer to God that God has not known (foreknown as we say in our time limited way), and for which He has failed to answer from an eternity. There is no more impious remark than “There is no use praying; everything is fated and fixed.”
Nihil obstat. *Rev. Weigand, Censor Deputatus
Imprimatur. *James Hartley, Bishop of Columbus