Here is a wonderful story, adapted from the Grimm Brothers Fairy Tales that illustrates beautifully the reason we ought to pray without ceasing.
There once was a sly, cunning old Fox that roamed the world. Once, during his roaming, he came to a meadow in which was a flock of fine fat geese. When he saw these fine fat geese he smiled and said to them, "I come at the nick of time, you are sitting together quite beautifully, so that I can eat you up one afte the other." The geese cackled with terror, sprang up, and began to wail and beg piteously for their lives. But the sly, cunning old Fox would listen to nothing, he had heard all the wails and begging before. He looked at them very cooly and said, "There is no mercy to be had! You must die."
One of the smarter geese mustered up her courage and said, "If we poor geese are to yield up our vigorous young lives, show us the only possible favor and allow us one more prayer, that we may not die in our sins, and then we will place ourselves in a row, so that you can eat us all up from the fattest to the thinnest." "Yes," said the Fox, "that is a reasonable request. Pray away, I will wait till you are done." Then the first began a good long prayer, forever saying, "Lord, have mercy!" and as she would make no end, the second did not wait until her turn came, but began also, "Lord, have mercy!" The third and fourth followed her, and soon they were all cackling together seeking mercy from their Maker.
When they have done praying, the story shall be continued further, but at present they are still praying, and they show no sign of stopping.