Twice a Day

Centering prayer is the keystone of a comprehensive commitment to the contemplative dimensions of the Gospel.  Two periods a day of twenty to thirty minutes -- one in the early morning and one halfway through the day or in the early evening -- maintain the reservoir of interior silence at a high level at all times. ... To find time for a second period later in the day may require special effort.  If you have to be available to your family as soon as you walk in the door, you might center during your lunch hour.  Or you might stop on the way home from work and center in a church or park.  If it is impossible to get a second period of prayer in, it is important that you lengthen the first one.

-- Thomas Keating, Open Mind Open Heart, 123