Prayer ; Does it make any difference?

I am reading this book by Philip Yancy. It has been very good and I highly recommend it.

A couple of things about prayer, first prayer should change us to the point where we accept God's sovereign will for our lives and second prayer should motivate us as God works through His creation including the actions of His people. God works in mysterious ways and has left His Holy Spirit to guide our prayers and draw us into communion with His Son.