From Mere Christianity by CS Lewis Book IV, Chptr. 7
"But we must not remain babies. We must go on to recognise the real Giver. It is madness not to. Because, if we do not, we shall be relying on human beings. And that is going to let us down. The best of them will make mistakes; all of them will die. We must be thankful to all the people who have helped us, we must honour them and love them. But never, never pin your whole faith on any human being: not if he is the best and wisest in the whole world. There are lots of nice things you can do with sand; but do not try building a house on it."