Q: I know that the mind should be quiet, relaxed and empty during centering prayer, but I unsure of what our state of mind should be like. Should the mind be fully aware and deeply attentive, or less so, like that state leading to a twilight sleep?
A: This issue about the mind is a frequent question. Let me address your various points specifically.
You said "I know that the mind should be quiet, relaxed and empty during centering prayer." This is actually not true, but a common misconception. The mind in Centering Prayer should simply go about its business processing, which is normally in the form of thoughts. Centering Prayer deals with how we respond to what is going on in the mind - by being detached from that ongoing activity for a certain amount of time. Thoughts are a normal, integral and inevitable part of the prayer, for they are giving us an opportunity to become aware we are engaged with them, let go and return to our sacred symbol, which represents our intention to be with God.
You go on to say, "but I am unsure of what our state of mind should be like.” Our intention is not to focus or alter our state of mind, but on our desire to consent to the presence and action of God.
You ask, "Should the mind be fully aware and deeply attentive, or less so, like that state leading to a twilight sleep?" In the prayer, we are practicing just being. Our tradition uses the term "resting" in the sense of resting in the arms of one's beloved. It is not a time of thinking but of being. We are alert and receptive, present to God.
The appropriate role of the mind happens before and after your Centering Prayer period – in noticing God present in your desire and yearning, and in the transformation happening in your life and in your relationships.