Personally, I don't think it was ever intended to be a prescription or some sort of mantra to be repeated over and over. I think Jesus was trying to tell them not to just repeat words that you are told to say and don't mean. As a kid I could have repeated the lords prayer by heart at the drop of a hat, yet I had no real idea what it meant nor had I given it any thought. I think Jesus had two points to make. Don't pray for show, and don't chant some **** (crep?) you have memorized but don't really mean, just talk to God from your heart in private. That is what I take away from Matthew 6: 5-8. Of course, the Church ended up turning the whole thing into a mindless chant for the masses.... to be repeated again and again mindlessly at mass.... like some sort of pagan incantation.
5 “And when you pray, do not be like the hypocrites, for they love to pray standing in the synagogues and on the street corners to be seen by others. Truly I tell you, they have received their reward in full. 6 But when you pray, go into your room, close the door and pray to your Father, who is unseen. Then your Father, who sees what is done in secret, will reward you. 7 And when you pray, do not keep on babbling like pagans, for they think they will be heard because of their many words. 8 Do not be like them, for your Father knows what you need before you ask him.