The saints speak of something they call the inextinguishable light. It is a light not of the eye but of the heart that never ceases to walk in purity and clearness. It swiftly leaves the darkness behind, and constantly strives towards the day's height. Its constant quality is to be continually purified. This is the light of eternity that can never go out, and that shines through the veil of time and matter. The saints never say that this light is given to them, but that it is given only to those who have purified their hearts in love for the Lord, on the narrow way which they have freely chosen.
~ from THE WAY OF THE ASCETICS by Tito Colliander