"Prayer is a war-time walkie-talkie, not a domestic intercom for ringing up the butler to change the thermostat. It is a war-time walkie-talkie to call in firepower because the enemy is greater than we are. If you try to turn this into a domestic intercom to bring another pillow, it malfunctions, and you wonder why. Its not made to be an intercom. Its made to be a war-time walkie-talkie" - John PiperThere are a few implications I haven't sorted through yet, but I really appreciate this perspective on prayer, because 1) it coincides closely with actual prayers in the Bible, 2) it removes any sense of selfishness from prayer, 3) it makes sense of passages like Jn 15:7,16 and Jm 4:1-3. Piper's imagery also helps solidify some other things: God's in command and has the over all plan / strategy. We are crucial to carrying out our assigned objective. If we are not carrying out our objective (building a bridge instead of blowing one up) or trying to carryout the objective some other way (taking out the bridge by throwing rocks at it because there are lots of rocks around and we are really good rock throwers) our prayers (more construction materials or more rocks to throw respectively) will not be answered.
I have one final thought that always tags along with prayer. We must know (or at least have a sense) of God's mission (globally, locally and personally) for our prayers to be effective. Is this a tall order? In one sense Yes. But in another sense No, because God's will in laid out in His Word. When we dive in and actually ask and seek and knock with the objective to know Him and what He wants to accomplish, He gladly lays it before us. Confusion is always from another source!
To God Alone be the Glory