The apparent shift from the sleep state to an awake one is actually quite subtle. There's no real line, except that there is! This subtlety is the reason that after an initial glimpse there can be so much trailing oscillation before we reach a real grounding, or stability, within Nondual awareness.
There's no such thing as "permanent" enlightenment, which is purely a mind-constructed idea that could only happen to a somebody, but there is certainly ongoing enlightenment, which has nothing whatsoever to do with a human being. Ongoing enlightenment--also known as abiding awakening--is unshakable and boundless.
Fred Davis, Awakening Clarity
This is REALLY good to know. Got it/Lost it has to come to an end at some point. ...ha,ha - just as spiritual egos need to disappear.