R. A. Torrey 
Power and Peace in Prayer [EPUB ebook] 

With startling and overwhelming force the tremendous importance of prayer is set forth in Ephesians 6:18: “Praying always with all prayer and supplication in the Spirit, and watching thereunto with all perseverance and supplication for all saints.”
When we stop to weigh the meaning of these words, then note the connection in which they are found, the intelligent child of God is driven to say, “I must pray, pray, pray. I must put all my energy and all my heart into prayer. Whatever else I do, I must pray.”
The Revised Version is, if possible, stronger than the Authorized: “With all prayer and supplication praying at all seasons in the Spirit, and watching thereunto in all perseverance and supplication for all the saints.”
Note the alls: “with all prayer, ” “at all seasons, ” “in all perseverance, ” “for all the saints.” Note the piling up of strong words, “prayer, ” “supplication, ” “perseverance.” Note once more the strong expression, “watching thereunto, ” more literally, “being sleepless thereunto.” Paul realized the natural slothfulness of man, and especially his natural slothfulness in prayer. How seldom we pray things through! How often the church and the individual get right up to the verge of a great blessing in prayer and just then let go, get drowsy and quit. I wish that these words “being sleepless unto prayer” might burn into our hearts. I wish the whole verse might burn into our hearts.Cross Reach Publications