Three Stages In the Practice of the Jesus Prayer

There are three stages of prayer. The first level is oral prayer or as it is often referred to, prayer of the lips. This is the beginning stage where the prayer is said aloud. This engages more of our brain and helps us to focus our attention on the words of the prayer. Here we discover the nature of our distracted mind and programming of our brain. We encounter our own thoughts that will ride on top of the words our prayer like a hitchhiker. We will also have the sensation that we are more than our thoughts as we gradually begin to know our soul. We find that we can actually observe our thoughts interfering with our prayer. We wonder, “Where do these thoughts come from?” At this stage prayer is still something external to us so we need to consider this as a first step.
More on oral prayer...

The second level is mental prayer. As we continue with prayer over a period of time we will find that we will be able to pray without using the lips and say the prayer silently in our mind. This will happen naturally. We don’t want to force it prematurely. Don’t try and be overzealous and end up like the hare instead of the tortoise. If we experience distraction at this level then simply go back to using oral prayer. Keeping our attention focused on the words of the prayer is essential. Theophan says that at this stage, "the mind is focused upon the words" of the Prayer, "speaking them as if they were our own." We begin to see how we can intercede and counteract our thoughts. We discover a new control center that we are beginning to see exists in our heart.

When you try and unite your mind with your heart the mind finds a hardness of the heart and cannot easily penetrate it. The mind will be frustrated and distracted by many other thoughts. As you begin to enter into mental prayer the words will be said in your mind and not your heart. This is where you need to expect to begin at this stage. Only later after much patience and effort will you be able to penetrate the heart. Try to keep your focus on the words as you pray and it will naturally open the door of your heart.
Advice from Elder Paisios on Hardness of the Heart

The third level is called prayer of the heart. At this level, prayer is no longer something you do, but something you are. This stage involves a transforming action as you discover your true nature. You find that you are much more than a body and brain, but that you are noetically connected with the divine energies of our God, and know that He dwells in the depths of your heart. This is not something you will be able to explain to others but you will recognize it. The prayer is now said continuously without any effort in the heart. This kind of prayer comes as a gift of the Holy Spirit. As Paul tells us, "God has sent the Spirit of his Son into our hearts, the Spirit that cries 'Abba, Father!'." (Gal. 4:6) At this stage we now know what it means to be in union with God. We feel the divine presence within and sometimes are connected with the vision of the uncreated light, which is the pure energy of God. We can experience the kingdom of heaven within each of us. At this stage the door of our heart is wide open and we find our lives transformed as we begin to live a life of love. We now can pray “without ceasing” (Eph 6:18; 1 Thes 5:17; 1 Tim 2:8; Rom 12:12; 1 Thes 2:13; 1 Tim 1:2) as Scripture instructs us.