Pray in the spirit at all times and on every occasion. Stay alert and be persistent in your prayers for all believers everywhere. Ephesians 6:18 

"The greater the difficulty to be overcome, the more  will it be seen to the glory of God how much can be done by prayer and faith." George Müller

“All believers are called upon, in the simple confidence of faith, to cast all their burdens upon Him, to trust in him for everything, and not only to make every thing a subject of prayer, but to expect answers to their petitions which they have asked according to His will, and in the name of the Lord Jesus.” 

“I saw that the most important thing I had to do was to give myself to the reading of the word of God, and to meditation on it. . . . What is the food of the inner man? Not prayer, but the word of God; and . . . not the simple reading of the word of God, so that it only passes through our minds, just as water runs through a pipe, but considering what we read, pondering over it, and applying it to our hearts.” 

“I believe God has heard my prayers. He will make it manifest in His own good time that He has heard me. I have recorded my petitions that when God has answered them, His name will be glorified.” 

“Be assured, if you walk with Him and look to Him, and expect help from Him, He will never fail you.” 

“No one ought to expect to see much good resulting from his labors in word, and doctrine, if he is not much given to prayer and meditation.”

― George Müller