Thomas Keating advises people over and over again not to look for the fruits of this prayer in their subjective experience of it.  Centering Prayer is not about accessing sublime states of consciousness or having mystical experiences.  The fruits of this prayer are seen in daily life.  They express themselves in your ability to be a bit more present in your life, more flexible and forgiving with those you live and work with, more honest and comfortable in your own being.  These are the real signs that the inner depths have been touched and have begun to set in motion their transformative work.

Cynthia Bourgeault, Centering Payer and Inner Awakening, pg. 14

In one of the very earliest training workshops, led by Thomas Keating, a nun tried out her first twenty-minute taste of Centering Prayer and then lamented, "Oh, Father Thomas, I'm such a failure at this prayer.  In twenty minutes, I've had ten thousand thoughts."
"How lovely!" Responded Thomas Keating without missing a beat.  "Ten thousand opportunities to return to God!"

Cynthia Bourgeault, Centering Payer and Inner Awakening, pg. 23-24