A few quotes from Paulo Coelho's Manual of the Warrior of Light that I love about the need for a touch of madness to be a warrior of the light, in other words to grow spiritually:
"The warrior knows that he is free to choose his desires, and he makes these decisions with courage, detachment and - sometimes - with just a touch of madness."
"The warrior of light does not worry that, to others, his behaviour might seem quite mad. He talks out loud to himself when he is alone. Someone told him that this is the best way of communicating with the angels, and so he takes a chance and tries to make contact. At first, he finds this very difficult. He thinks that he has nothing to say, that he will just repeat the same meaningless twaddle. Even so, the warrior persists. He spends all day talking to his heart. He says things with which he does not agree, he talks utter nonsense. One day, he notices a change in his voice. He realises that he is acting as a channel for some higher wisdom. The warrior may seem mad, but this is just a disguise."