"...between...times of devotion, labor to be much in ejaculatory prayer. While your hands are busy with the world, let your hearts still talk with God; not in twenty sentences at a time, for such an interval might be inconsistent with your calling, but in broken sentences and interjections. It is always wrong to present one duty to God stained with the blood of another, and that we should do if we spoiled study or labor by running away to pray at all hours; but we may, without this, let short sentences go up to heaven, ay, and we may shoot upwards cries, and single words, such as an "Ah," an "Oh," an "O that;" or, without words we may pray in the upward glancing of the eye or the sigh of the heart. He who prays without ceasing uses many little darts and hand-grenades of godly desire, which he casts forth at every available interval. Sometimes he will blow the furnace of his desires to a great heat in regular prayer, and as a consequence at other times, the sparks will continue to rise up to heaven in the form of brief words, and looks, and desires."
From Charles Spurgeon's sermon "Pray Without Ceasing."