Prayer is always a movement, a murmuring of the Holy Spirit in the heart. According to the teachings of the spiritual Fathers and Mothers of the Church, the mere intention to pray is already prayer.
Saint Seraphim of Sarov says that “we do not cease calling upon the Holy Spirit, but when God is in us, we no longer need to invoke Him. In true prayer, it is no longer I who pray, but the Holy Spirit who prays in me.”
In the letters of Saint Paul, two passages — which resemble each other and complete one another — describe the mysterious action of the Holy Spirit in the human heart. “What you received was not the Spirit of slavery; you received the spirit of adoption, enabling us to cry out, ‘Abba, Father!’” (Rom 8:15). “God has sent into our hearts the Spirit of the Son crying, ‘Abba, Father!’” (Gal 4:6).
So closely akin are prayer in the Spirit and prayer of the Spirit in us, that in reality, it is hard to differentiate between the two. There is no tangible boundary, formal or rational. The two blend, but without a fusion, of being with the Holy Spirit.