The repetition is not a repeat of a prior prayer period. We are not returning to gain new insights or knowledge. Nor are we returning to try to 'do better' or 'get it right' as when revising for an exam. Instead, the repetition is a move toward a more simple, receptive and personal prayer.
You decide what to repeat by your response to the material of the previous prayer, not by the material itself. You return to the place in the last prayer where you were most moved.
The movement may have been an experience of joy, hope, forgiveness, kindness, compassion, closeness, intimacy, attraction, or consolation. You may have experienced sadness, confusion, animosity, intolerance, repulsion, or desolation.
Your response may have been light or heavy, warm or cold, positive or negative. The 'tone' doesn't matter. What matters is that you notice the inner movements that occurred so that you can return to the most significant.
Pay particular attention to any desires that arose during the prayer. I'll say that again as this is important. Pay particular attention to any desires that arose. God may have touched something deep.
For example, you may notice you felt a desire for love. Why did this desire arise? Perhaps you feel unloved, rejected, alone? Or maybe it's an invitation to give your love to others? Returning to the material that gave rise to this desire, and praying through it again, may provide clarity as to what is happening deep within you.
Returning to what moves and stirs you will make the prayer personal. What moves you in a passage of scripture may not touch me. Therefore, these movements reveal what is meaningful to you, and how God is gently leading you. They help you discern your deepest desires, which are God’s desires for you.
The first prayer may have had a lot of content. There may have been many people, places, objects, dramas, words and actions in the story. In the repetition, you simplify the prayer by returning to what touched you. The steps are as follows.
Recall the scene or words that gave rise to the feelings or thoughts that were most significant to you. The material that drew you most. The movements that touched you most or were strongest. Remember, these could be positive or negative, both are of equal value.
Return to the material that caused this movement and relive it.
Be receptive to God's presence and action and let him take you deeper if he wishes. Do not strive to make this happen, that is God's role.
Let me give you an example of the repetition in action. I was once praying with a paraphrase of Psalm 139 that someone had rewritten as a prayer in the first person. It started, as usual, acknowledging God knows all we do, then said, "Father, you know when I'm loving and selfish, succeed and fail, and yet you love me more than I will ever know". What hit me was the phrase "and yet".
And yet God loves me? This phrase disturbed me. That disturbance was an internal movement. It wasn't pleasant, but something was happening within me in response to the simple phrase "and yet".
I used the repetition on just this phrase, simplifying the prayer, and allowed the disturbance to surface again. Once it had, I quietly sat with the disturbance. I let it penetrate me so I could fully experience it and let God take me deeper. As I sat with it, I realised the disturbance was disagreement with the statement "and yet". "And yet" implied that the Psalmist expected God's love to be conditional. He expected God to love him when he loved, but not when selfish; when he was successful, but not when he failed. He seemed surprised that God’s love was unconditional.
So why was I drawn to this? What could God be highlighting? I believe God was showing me that I now understood his love. I say 'now' because this wasn't always the case. In the past, I'd thought love was conditional. This later gave way to an understanding similar to that of the Psalmist's, that God loved me even when I was selfish or failed. But my understanding of unconditional love had now moved. I now believed that God had never view me as blemished and imperfect, that was my view of myself.
No love is conditional; not even human love. I have always loved my son and always will. He has never been blemished and imperfect in my eyes. Some of his choices and actions have not been 'good' for himself or others. But do you know what I felt toward him during these times? Love. My love caused me to hurt because he hurt. I felt the pain of the remorse he felt. I cried when he cried. I suffered because he suffered.
I now know God's love is stronger than mine. That he can show as much goodness and compassion as me (Matthew 7:11; Luke 11:13). And that he still sees the original goodness in his sons and daughters (Genesis 1:31), as I do in mine. This is the fruit of the prayer repetition.
 Please note, I’m not trying to teach you correct theology here. I’m telling you what the passage said to me personally.