About Savitri | B1C1-20 Transition from the Sleep to Waking (p.9)

The Power that kindles mind was still withdrawn:
Heavy, unwilling were life’s servitors
Like workers with no wages of delight;
Sullen, the torch of sense refused to burn;
The unassisted brain found not its past.
Only a vague earth-nature held the frame.
But now she stirred, her life shared the cosmic load.
At the summons of her body’s voiceless call
Her strong far-winging spirit travelled back,
Back to the yoke of ignorance and fate,
Back to the labour and stress of mortal days,
Lighting a pathway through strange symbol dreams
Across the ebbing of the seas of sleep.

It is the description of how the Consciousness works its way back, bringing back remembrance, waking the faculties — more conscious in the night than in day, because the inner being is more active.  As the body goes to sleep, the inner being wakes up and, with it, comes back the memory of the past.
For those who are more developed in the inner being than in the body, those that came down upon earth fully conscious and had their consciousness veiled and dulled down by the contact with the Matter, the sleep is often a revelation. Because the body is asleep, inactive, then the inner consciousness is more free, and in contact with what it knows more directly.
For this all those who have come down upon earth fully developed and fully conscious, in the night when the body rests, they remember what they were and what they can do. And in fact, they actually continue to do it in the night when their body is immobile. They continue their activity and they do what they came upon earth for doing, even before the body knows and can help in the work.