Centering Prayer can be compared to a cow chewing their cud. Actually, I always found that image rather disgusting visually but the idea of chewing something over and over again to receive all the nourishment it holds is a useful image. In the Western Christian tradition of meditation, Abba Isaac taught the use of these words from the Psalms:
“0 God, come to my assistance; 0 Lord, make haste to help me”