“Now if we are children, we are heirs—heirs of God and co-heirs with the Messiah—if, in fact, we share in his sufferings in order that we may also share in his glory.”
– Romans 8:17 (ISV)
As I was investigating the use of prayer (I’m still looking into it) I came across the following views (of which I published the best parts):
‘When God gave us dominion over the earth, he placed himself in a moral position where he must respect our wills before he acts in our sphere of responsibility. The Psalmist tells us, “The heavens are the heavens of the Lord; But the earth He has given to the sons of men.”  Since the earth is now our area of dominion , God must have our permission before he interferes with our stewardship. This is not a situation we forced on God, but a position he brought upon himself by committing the dominion of the earth to human beings.  This is where agency becomes important. Agency is acting on behalf of another party. Unless we invite God to be involved in our sphere of responsibility, he is morally restricted as to what he can do. This means we can use our wills to place God in a moral situation where he can do more than he could have before we made the choice. This agency can come in the form of obedience, prayer, praise, worship, thanksgiving, spiritual warfare, etc. Of course, this agency also means we can restrict God from acting if we refuse to ask his help.  Probably the most obvious example of this is God’s desire to save those who are lost. He is not willing for any to perish, but if they do not repent, he must allow them to go to hell. In this most important of all human decisions, God is limited by the free will of man. ’
– Michael R. Saia, Does God Know The Future, Chapter 12: Prayer and Absolute Foreknowledge, Why is Prayer Necessary?, p245-246 (This book is now available for free in my webstore! Click here to visit it!)
‘God will not go over the Church’s head to do things in spite of her because this would abort His plan to bring her to full stature as co-sovereign with the Son. He will therefore do nothing without her. To this John Wesley agrees when he says, “God does nothing but in answer to prayer.” (…)
He [God] has given to her [the Church] “power of attorney.” She is His “deputy.” But this delegated authority is wholly inoperative apart from the prayers of a believing Church. (…)
As in the case of Adam, God saw that it was not good for His Son to be alone. From the very beginning it was God’s plan and purpose that out of the riven side of His Son should come an Eternal Companion to sit by His side upon the throne of the universe as a bona fide partner, a judicial equal , to share with Him His sovereign power and authority over His eternal kingdom. “Fear not, little flock, for it is your Father’s good pleasure to give you the kingdom” (Luke 12:32).’
– Paul E. Billheimer, Destined for The Throne, p17-18, 26 (footnote p 31)
 Psalm 115:16
 See also Genesis 1:26-28.
 Please refer to these references for instances where human wills affected God: Genesis 18:22-33; Exodus 32:9-14; II Kings 20:1-7; Isaiah 5:1-7; Jeremiah 18:5-10; 26:1-3; Ezekiel 22:30, 31; Jonah 3:5-10; Amos 7:1-6; James 4:2. See also these references to God’s will not being done because of the will of man: Matthew 23:37; Mark 6:5, 6; Luke 7:30; I Thessalonians 4:3; 5:18; I Timothy 2:4; II Peter 3:9; Matthew 6:10.
 Refer also to these references giving conditions for answered prayer: I John 5:14, 15; Mark 11:23, 24; John 16:23, 24; I John 3:22; James 5:16; Psalm 66:18; John 15:7; I John 3:24; James 4:2,3; John 15:16. If there are conditions for answered prayer, then the will of man must affect God such that he is free or restricted in answering prayer, depending on what we choose.
 There are two common alternatives offered to the position that God is dependent on the free will of man. The first alternative is that God determines what we will choose, but we are still free to choose it. This notion of “contingent certainties” or “fixed freedom” is blatantly illogical, as has been shown in chapter 4. The second, that God determines who will be saved or lost and man has nothing to do with it, makes salvation entirely God’s doing, with people perishing and going to hell because God wills it so. This is an affront to the justice of God, who is not willing that any should perish, but that all should come to repentance.
 Judicial – “allowed, enforced or set by order of a judge or law court” (Webster’s New World Dictionary). The equality which is here in view is a delegated equality. Although it is a delegated equality, it is as fully recognized and respected as if it were original. This delegated equality is unmistakably implied in the term “joint heir” (Rom. 8:17). In law a joint heir can do nothing alone, nothing without the other.