Meditation….day and night.

“But his delight is in the law of the LORD,
   and on his law he meditates day and night. (Psalm 1:1-2)

Meditation: “The practice of reflection or contemplation. The word meditation or its verb form, to meditate, is found mainly in the Old Testament. The Hebrew words behind this concept mean "to murmur, "a murmuring," "sighing," or "moaning." This concept is reflected in Ps 1:2, where the "blessed man" meditates on God's law day and night. The psalmist also prayed that the meditation of his heart would be acceptable in God's sight (Ps 19:14). Joshua was instructed to meditate on the Book of the Law for the purpose of obeying all that was written in it (Josh 1:8).” (from Nelson's Illustrated Bible Dictionary, Copyright © 1986, Thomas Nelson Publishers)

I like the thoughts on meditation from Matthew Henry's “Commentary on the Whole Bible.”

“To meditate in God's word is to discourse (dialogue) with ourselves concerning the great things contained in it, with a close application of mind, a fixedness of thought, till we be suitably affected with those things and experience the savour and power of them in our hearts. This we must do day and night; we must have a constant habitual regard to the word of God as the rule of our actions and the spring of our comforts, and we must have it in our thoughts, accordingly, upon every occasion that occurs, whether night or day. No time is amiss for meditating on the word of God, nor is any time unseasonable for those visits. We must not only set ourselves to meditate on God's word morning and evening, at the entrance of the day and of the night, but these thought should be interwoven with the business and converse of every day and with the repose and slumbers of every night. When I awake I am still with thee”