while many have seen {the light of God}, they have not all acquired it, just like many have seen the great treasure in the royal vaults and have gone away empty. While a divine light and illumination often comes in the beginning to those who are fervently repenting, it passes away immediately. If they give themselves up even to death itself and seek it with hard labor, presenting themselves to the Lord as worthy and blameless in every way, then at last they receive it again come back to them. If however, they become a little lazy and take leave from throwing themselves into greater labors by loving their own souls, they become unworthy of so great a gift and do not enter, while still living in the body, into everlasting life.

(Saint Symeon the New Theologian)