R. A. Torrey 
How to Pray [EPUB ebook] 

In the 6th chapter of Ephesians in the 18th verse we read words which put the tremendous importance of prayer with startling and overwhelming force:
“Praying always with all prayer and supplication in the Spirit, and watching thereunto with all perseverance and supplication for all saints.”
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,
must pray, pray, pray. I must put all my energy and all my heart into prayer. Whatever else I do, I must pray.”