Prayer According to God's Will

I'm reading the Bible in one year and the New Testament reading for Dec 5 is 1 John 5:1-21.

"This is the confidence we have in approaching God: that if we ask anything according to his will, he hears us." - 1 John 5:14 (NIV)

Do our prayers simply change us and align us to God's will, without having any bearing on His will? (Then why pray? For example, why pray for the salvation of the lost if the lost are saved completely apart from our prayers?)

Do our prayers have a bearing on God's will to the extent that our prayers determine His will? (Then what if two people pray against each other? For example, what if one person prays for sunny weather and another person prays for rainy weather?)

Or do our prayers provide the means by which God, knowing what we would pray for and how He would answer accordingly (be it yes or no), accomplishes His will - His good, pleasing and perfect will?

God answers prayer! He will answer yes when answering yes is for the best; He will answer no when answering no is for the best. And whether He answers yes or no, His will is exactly what we would desire if we knew all the facts.

Links: Prayer Changes Things (26 Nov 10), A Molinist View of Prayer (31 Dec 10)