In Psalm 127:1, this signifies a clear and alert state. (Arcana Coelestia 5210)

When a man begins to know that he does not live from himself, he wakes up. (Arcana Coelestia 147)

5210. 'And he fell asleep' means a state of obscurity. This is clear from the meaning of 'sleeping' as a state of obscurity. 'Sleep' has no other meaning than this in the spiritual sense, even as 'wakefulness' means nothing else than a state of brightness; for spiritual sleep is a time when truths remain in obscurity, spiritual wakefulness when truths exist in brightness. And to the extent that truths are in the one state or else the other, spirits are awake or asleep. From this it is evident that 'falling asleep' is a state of obscurity.