To pray unceasingly as St. Paul asks us to do would be completely impossible if it meant to think constantly about or speak continuously to God. To pray unceasingly does not mean to think about God in contrast to thinking about other things, or to talk to God instead of talking to other people. Rather, it means to think, speak, and live in the presence of God.
Although it is important and even indispensable for the spiritual life to set apart time for God and God alone, prayer can only become unceasing prayer when all our thoughts – beautiful or ugly, high or low, proud or shameful, sorrowful or joyful – can be brought and expressed in the presence of God. Thus, converting our unceasing thinking into unceasing prayer moves us from a self-centered monologue to a God-centered dialogue. This requires that we turn all our thoughts into conversation. The main question, therefore, is not so much what we think but to whom we present our thoughts.
Prayer is an outward, careful attentiveness to the One who invites us to unceasing conversation.
Prayer is the joyful affirmation that God knows our minds and hearts without anything being hidden.
From Spiritual Direction: Wisdom For The Long Walk of Faith