Canute got carried away by pride, did he not?
The question may be what kind of things do we have the right to pray for? We have discussed this verse from Isaiah before, so I know we agree the KJV is not wrong.
Isa 45:11 Thus saith the LORD, the Holy One of Israel, and his Maker, Ask me of things to come concerning my sons, and concerning the work of my hands command ye me.
I think Jesus was saying something similar here:
Jhn 16:13 Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come.
Something may look good to me but I might not see the bigger picture. It might be good for me but bad for other people. One night recently, I found I did not know how to pray or even what to ask for. I said to myself, "Jesus knows what I should ask for. Maybe I don't even need to know. I can just pray and ask for whatever he wants." Lately my spiritual senses haven't been the best; but when I did pray like that recently, I could sense a tremendous movement of angels going to do what Jesus wanted. It did come to me that many people in the world have minds that are darkened and many of them would accept the Light of God if they knew about it, so then I prayed for them specifically -- that those who were in darkness but ready to receive Light might receive it. All truth? It was all the truth I needed to know in that case. I may be going a bit off topic though.
What seems certain to me is that if someone has heard from God that something is His will, it will surely come to pass if he prays for it. Those person is exercising the lawful dominion over the earth given to man, and Heaven will surely back him back. IF he gives a prophecy, it is more than a prediction -- a prediction is a guess the way fortune telling is a guess-- a real prophecy is more than a guess, God will make it happen.
It is possible, surely it is, that a prophet can hear something from God but not hear it completely clearly. He may be uncertain about what it means. He should not be saying, "Thus saith the Lord" in such cases.
A prophet may also tune in wrong messages if he's not careful. Those will lack the "certainty" that should be present when it's really the Spirit relaying a message. That kind of uncertainty can also be caused by a lack of spiritual alertness of the person.