The cells of the human body are constantly being renewed; each day old worn out cells are replaced by new ones. This process of renewal is spread over seven years.
So, after seven years the body’s cells have been replaced, but that does not mean that the person has become a new being. The cells possess in effect a kind of memory, which they transmit in the form of etheric imprints to the replacement cells.
Thoughts, feelings and energies circulate on these imprints as if along well marked out grooves and circuits, and they inherit this memory. This is why most humans continue to think in the same way and repeat the same mistakes: the new cells are subject to the influence of the old memory.
Anyone who truly wants to change must change the memory in their cells; in other words, as the new cells replace the old ones they must do all they can to imbue them with more elevated thoughts and feelings.
For, even if they receive a spiritual teaching, they will not change deep down until they put their inner world in order.