Memory and oblivion signify for the ego what waking and sleeping signify for the astral body. Just as sleep permits the cares and troubles of the day to disappear into nothingness, oblivion spreads a veil over the bad experiences of life, blotting out a part of the past. Just as sleep is necessary for the restoration of the exhausted life forces, so man has to eradicate certain parts of the past from his memory if he is to approach new experiences freely and without bias.
But precisely through forgetting, strength develops for perception of the new. Consider certain facts, like that of learning to write. All the details the child has to experience in learning to write are forgotten. What remains is the ability to write. How would man be able to write if at every stroke of the pen all the past experiences in learning to write were to arise again in the soul as memory?
Source: Rudolf Steiner – GA 13 – An Outline of Occult Science: II: THE ESSENTIAL NATURE OF MANKIND
Translated by Maud and Henry B. Monges and revised for this edition by Lisa D. Monges