I have been reading Jeremy Walker’s The Brokenhearted Evangelist  and in that book he includes a powerful section dealing with the importance of prayer in the practice of evangelism. After quoting John Sutcliff, who cries out against lukewarmness, Walker asks and answers this question: How do we keep our prayers fiery?
How do we keep our prayers fiery? By engaging in hand-to-hand combat with Satan’s hosts, for those who are yet under his dominion. Why do we keep our spiritual weapons sharp? So that we can fight. How do we learn how to use those weapons? When we engage with lost men. Where are our graces brought to their highest pitch and exercised to their greatest degree? It is often when we are locked in mortal combat for the salvation of a soul. Where are our minds fired with holy truth so that we begin to understand, to press, and to be in earnest? When are our hearts most ablaze with love for Jesus Christ? When, in short, are we most alive as Christians? With the possible exception of the gatherings of the saints for worshiping God, it is when we are involved in the life business of the redeemed men and women of Jesus Christ, engaging with transgressors and seeking their salvation for the glory of God in Jesus Christ. There is little that so elevates us—that so engages the totality of our redeemed humanity—as the holy cut and thrust of evangelism. Nothing so casts us upon the grace of God in Jesus Christ. Nothing so reminds us of our need and sends us in desperation to God for increased measures of His Spirit as the reality of wrestling for souls.