On Prayer by E. M. Bounds

Great incentives to pray are furnished to Holy Scriptures and our Lord closes his teaching about prayer, with the assurance and promise of heaven.  The presence of Jesus Christ in heaven, the preparation for His saints which he is making there, and the assurance that He will come again to receive them--how all this helps the weariness of praying, strengthens its conflicts, sweetens its arduous toil! These things are the star of hope to prayer, the wiping away of its tears, the putting of the odor of heaven into the bitterness of its cry.  The spirit of a pilgrim greatly facilitates praying .  An earthbound, earth-satisfied spirit cannot pray.  In such a heart, the flame of spiritual desire is either gone out or smoldering in faintest glow.  The wings of its faith are clipped, its eyes are filmed, its tongue silenced.  But they, who in unswerving faith and unceasing prayer, wait continually upon the Lord, do renew their strength, do mount up with wings as eagles, do run, and are not weary, do walk, and not faint.