Why say the Jesus prayer

A Protestant friend asked me why we say the Jesus prayer. Here is part of my response in our ongoing conversation:

When we petition God, we forget the words of Jesus that God already knows what we need before we ask. So the more fundamental problem is our fear and doubt and misdirected attention and passionate urges and bombarding thoughts ( logismoi). The Jesus prayer is just the most popular form of a prayer technique (or better, a way of prayer) that shifts our focus away from the problems (that we don't understand anyway) and away from telling God what to do about them toward a calling to mind of who God is and an appeal for mercy. Thus every need that may come to my mind or dwell in my heart is the object or recipient of that mercy. My mind free from having to figure out what to tell God to do, I can focus my attention on my heart (my inner, peaceful place where Christ dwells) so that I can attend to that peace.  

The Jesus prayer helps us abide in Christ. It helps us discern what are mere logismoi and what are true promptings of love and of the Holy Spirit (which is, in the end, the same thing).