"When you are praying, do not heap up empty phrases as the Gentiles do; for they think that they will be heard because of their many word." Matthew 6:7
Keep it simple are Jesus' words of instructions to the disciples. Bread, forgiveness, and keeping us safe all require us to make our requests simple. Life sustaining, care for the other, and care of us are simple requests. It also asks us not to lose sight of one another. In asking for forgiveness we are to recall those who we owe an apology to. In praying simple words we actually get to what is really on our hearts and minds instead of what we think other people want to hear.
Who hears it is Jesus' other point. Are we actually praying to God or praying to others? Are we praying so that we will be recognized for our wonderful words or are we exposing our hearts to God? Direction is what is thought of here. When we pray so that we feel comfortable with what others are hearing we have lost who we should be praying too. We have become distracted into thinking not conversing with God.
Prayer is our line of communication with God. It opens up our relationship to God. When we keep it simple it is more like a relationship fostered with a friend. We don't think of the words we use with our friends in conversation because it is familiar and intimate. This is what Jesus is saying about our prayers to God. Let them be familiar to you, don't worry about what others think of your prayer. Prayer is about you and God.