Take the process of learning to write. What really happens before the moment when we are able to put pen to paper and express our thoughts in writing? A great deal must have happened — a whole series of experiences, from the first attempt to hold the pen, then to making the first stroke, and so on through all the efforts which lead at last to a grasp of the craft of writing. If we recall everything that must have occurred during months or years, and all we went through, perhaps by way of punishments and reproofs, until at last these experiences were transformed into knowing how to write, then we must say: These experiences were recast and remoulded, so that later on they appear like the essential core of what we call the ability to write.
Spiritual Science shows how this transformation comes about. It is possible only because human beings pass repeatedly through the condition of sleep. In daily life we find that when we are at pains to absorb something, the process of imprinting and retentions is considerably aided if we sleep on it; in that way we make it our own. The experiences we go through have to be united with the soul and worked on by the soul if they are to coalesce and be transformed into faculties. This whole process is carried through by the soul during sleep, and thereby our life is enhanced.
Source: Rudolf Steiner – GA 58 -Metamorphoses of the Soul / Paths of Experience – Volume One: Lecture 5: Human Character – Munich, 14th March 1909
Translated by C. Davy and C. von Arnim