A memory is what is left when something happens and does not completely unhappen.
This is quote from Edward de Bono. I can understand the first part. 'what is left when something happens', but I can't understand latter part. I thought 'unhappen' means opposite of happen, but it doesn't seem like fitting here.
It seems to me 'A memory is what is left when something happens and something happens'. and I don't think it is the meaning of that sentence.
Could it be 'does not cease to happen' or 'you can not forget' something? I googled it but all I got is exact quote, not the explanation.