The Greek myth of Orpheus and Eurydice tells a tale of wild love gone wrong. Orpheus, the world's greatest musician, who with his harp and his voice could "soothe the savage beast" and melt even the rocks, falls hard for the stunning Eurydice. Eurydice, alas, is bitten by a venomous snake, and dies, drifting off to the underworld. Orpheus travels there and sings songs of such rending grief that even Hades, the lord of the dead, is moved, and tells Orpheus that Eurydice will follow him back to the the land of the living on one condition: that he not look back even once.
Of course, all along the walk back Orpheus does not hear Eurydice behind him, and, just a few steps from the exit, he is irresistibly drawn to look back to make sure she is there. And poof -- Eurydice, who has been following him, silent as a shadow the entire time, is instantly and forever whirled back to Hades.
The same idea of not looking back is echoed in many other legends and cultures.
In the Old Testament, Lot and his wife are spared from the destruction of Sodom and Gomorrah on the condition that they not look back. Lot's wife looks back, unfortunately, and is instantly transformed into a pillar of salt.
In the New Testament, Jesus is asked by a disciple for leave to bury his dead father. "Let the dead bury the dead," Jesus replies. Don't look back.
In another Greek mythology, that of Psyche and Cupid, Cupid -- an incredibly beautiful god of love -- makes Psyche his wife and sleeps with her on condition that she never look upon him. She defies him and he flees. (She then has to undergo a long series of trials to win him back.)
And this not looking back speaks to a larger point -- the idea of spiritual awakening being a blindness to the ordinary world.
Oedipus, who out of ignorance weds his mother and kills his father, blinds himself out of shame when he finds out the truth. But in his blindness he then gains spiritual power.
Tiresias, yet another figure of Greek literature, is a blind prophet. Again, the blindness to the ordinary world enables a seeing of the extraordinary.
You cannot see the Medusa without being petrified, the Greek hero Perseus knew. He had to see her through a mirror in order to slay her.
And in Indian philosophy,
The man of restraint is awake in that which is night for all beings; the time in which all beings are awake is night for the sage who sees. --Bhagavad Gita (2:69)
So what's going on here? Why all these references to not-seeing as being so important? Don't look, don't see, don't experience?
There are actually two separate but related concepts at work.
First, the Absolute, the Self, cannot be made an object of thought. The mind, which tries to make objects out of everything, which tries to consume everything, which tries to make out of everything an object of desire -- as soon as it tries to do with the Self, that Self flees (or appears to, anyhow). The mind must humbly keep its glance down, must forbear from appropriating, from taking credit, from trying to control, from attempting to assimilate, which is its normal course of action with everything.
Look not directly at the great, the awesome, the appalling, the monstrous, the miraculous. See it only, at most, through a reflection. See it only, as the wise one does, as an ordinary man experiences deep sleep -- something which is beyond the normal land of distinctions.
Second, there's the point that the Absolute brooks no compromise. When you are paying attention to relative life: to the past, to regrets, to worries... you are not paying attention to the Self. In the final analysis, every trace of individuality must be surrendered before it can be reborn anew. As the Bible says, one cannot serve two masters at once. In turning to the big Self, one must turn away from the little self. And this turning to the big Self is not about "seeing" or "experiencing" it but about renouncing that very mode of experience which seeks to see in that normal fashion.
Of course, in reality, this is not a one-time choice, but a trial that must be undergone and failed many times by the seeker before it finally sinks in. One loses Eurydice thousands or millions of times before one learns not to look back.