Where does the secret strength of faith lie? It lies in the food it feeds on; for faith studies what the promise is-an emanation of divine grace, an overflowing of the great heart of God. And faith says, "My God could not have given this promise except from love and grace; therefore it is quite certain His Word will be fulfilled." Then faith thinks, "Who gave this promise?" It considers not so much its greatness as, "Who is the author of it?" She remembers that it is God, who cannot lie-God omnipotent, God immutable-and therefore concludes that the promise must be fulfilled; and onward she proceeds in this firm conviction. She remembers why the promise was given--namely, for God's glory--and she feels perfectly sure that God's glory is safe, that He will never stain His own insignia, nor spoil the sparkle of His own crown; and therefore the promise must and will stand.
Then faith also considers the amazing work of Christ as being a clear proof of the Father's intention to fulfill His word. "He who did not spare his own Son but gave him up for us all, how will he not also with him graciously give us all things?"1 Moreover, faith looks back upon the past, for her battles have strengthened her, and her victories have given her courage. She remembers that God has never failed her, that He never once failed any of His children. She recalls times of great peril when deliverance came, hours of awful need when as her day her strength was found, and she cries, "No, I never will be led to think that He can change and leave His servant now. Thus far the Lord has helped me, and He will help me still."
Thus faith views each promise in its connection with the promise-giver and, because she does so, can with assurance say, "Surely goodness and mercy shall follow me all the days of my life!"2
Missionaries in foreign countries prepare by learning a new language, finding out about that country’s culture, and researching the physical needs of the area. You can do the same thing wherever you are.