You should not vacillate in your enthusiasm for practice. If you sometimes practice and sometimes do not, that will not give birth to certainty in the dharma
. Therefore, don't think too much. Just concentrate one-pointedly on mind training.
From Training the Mind & Cultivating Loving-Kindness by Chogyam Trungpa , copyright 1993 by Diana Mukpo.
(Official Chogyam Trungpa Website)
Published by arrangement with Shambhala Publications, Inc., Boston.
This site provides an on-line database of commentaries on the Tibetan Buddhist meditation practices of lojong (Mind Training) and tonglen.