I am still reading the great classic Pilgrim's Progress. In Chapter 14 Christian follows a man by the name of Vain Confidence, who leads them off the path. Vain Confidence falls into a pit which kills him leaving Christian and his companion Hopeful on their own and off course. When they realize that they are definitely off course they try to head back the way they came only it is dark and there is a storm raging about them. Unfortunately, they wind up at Doubting Castle and fall into the hands of Giant Despair and his wife Diffidence who throw them into their dungeon. Here below is a quote from the book toward the end of the chapter.
"So when morning came, the Giant went to them again, took them into the castle yard, and showed them what his wife had suggested to him. "These," said the Giant "were once Pilgrims as you are, and they trespassed on my property as you have done. When I saw fit, I tore them in pieces, and within ten days I'll do the same to you. Go! Get yourselves down to your cell again!"
With that, he beat them all the way there. They lay, therefore, all day on Saturday in a pitiful condition as before. When night came, and when Diffidence and her husband the Giant had gone to bed, they began again their conversation about their prisoners. And then the old Giant wondered why he couldn't bring them to an end with either his beating or his advice. Then his wife replied, "I fear that someone will come to rescue them, or that they may have some means to pick the locks by the means of which they hope to escape."
"You think so, my Dear?" said the Giant. "Therefore, I'll search them in the morning."
Well, on Saturday about midnight the prisoners began to pray, and they continued in prayer until almost daybreak. A little before dawn good Christian, as someone half amazed, broke out in this passionate declaration: "What a fool I am," he exclaimed, "to lay here in a stinking dungeon, when I could just as easily walk at liberty! In my coat, next to my heart, I have a Key called Promise. I'm persuaded it will open any lock in Doubting Castle."
"That's good news, Brother," said Hopeful. "Take it out and try."
Then Christian took it from his heart and began to try it on the dungeon door. As he turned the key, the bolt on the door gave way, and the door easily flew open. Christian and Hopeful both went out, and then Christian went to the iron gate, for it had to be opened too. Well, that lock turned very hard, but the key opened it. Then they threw open the gate to quickly make their escape."
This shows that we need to keep the word of God tucked in our hearts. And when we fall into doubt or despair (as most of us will) we need to use the word of God and His precious promises to help us escape.