Whatever your mind serves you up is just fine.  If you sink immediately into such depths of stillness that when the bowl bell is rung at the end of twenty minutes, it seems like only a minute, great!  You've had an easy and blessed time of it.  If every minute feels like twenty and you've been bedeviled by thoughts more prolific than the heads of Medusa, but still you've been doing your best to let them go and return to the openness, great!  You've gotten a good aerobic workout of your "muscle" of surrender.

...For the moment it's enough simply to reiterate Thomas Keating's reassurance that "the only thing you can do wrong in this prayer is to get up and walk out."  To sit there and quietly continue to do the practice, even if you perceive your efforts as totally unsuccessful, is, in his words, to know what it means to "consent to the presence and action of God within us" in whatever for it comes.  The power of this prayer lies in the consent.

Cynthia Bourgeault, Centering Payer and Inner Awakening, pg. 24-25