God's Plan?

This came up during a conversation with a friend tonight.  We were debating the value of petition prayers in light of God having a plan for us all.  I mentioned that even Jesus petitioned his Father in the Garden of Gethsemane.  "My Father, if it is possible, let this cup pass from me; yet not as I will but as you will." Mt 26, 39.   To my friend's point, where is the value of Jesus' prayer here?  Wasn't God's plan already set in motion?

If God has good things planned for us, do we need to request them in prayer?  Can we sway God's mind with our petitions?  If so, does that mean God's original plan was flawed, or can God simply change his mind?  Toss a little "free will" into the mix and it really starts you thinking (though I'm certain all of this has been debated, dissected, and documented over the centuries and it is just a matter of me finally covering it in a future class - but in the meantime it sure is intriguing to think about on your own).  

Maybe God has a decision tree, or a risk mitigation plan, or a contingency plan, you know, for those times when I throw him a curve ball and exercise my free will in a way not consistent with his teachings.  Maybe it is a contingency plan that gets executed when we don't petition our Father as he wants us to do so.

My friend and I ended our call somewhat where we started, him still wondering the value, and me not having an answer - yet.

Peace,