The soul is all light; darkness is caused by the deadness of the heart; pain makes it alive.
Commentary by Hazrat Inayat Khan:
Those who have avoided love in life from fear of its pain have lost more than the lover, who by losing himself gains all. The loveless first lose all, until at last their self is also snatched away from their hands. The warmth of the lover's atmosphere, the piercing effect of his voice, the appeal of his words, all come from the pain of his heart. The heart is not living until it has experienced pain. Man has not lived if he has lived and worked with his body and mind without heart. The soul is all light, but all darkness is caused by the death of the heart. Pain makes it alive. The same heart that was once full of bitterness, when purified by love becomes the source of all goodness. All deeds of kindness spring from it.