When a person has to pass from one level of existence to another, one of the rites of passage is the forgetting of what he knows of the past.
If he does not do so, he is liable to get mixed up and his appreciation of the new experience will be weakened, if not distorted, especially if there is some relation between the two levels.
As in learning a new language, the old has to be functionally forgotten or discarded; otherwise, there would be a tendency to mix them up.
Every experience leaves an impression that has to be wiped out, more or less, in order to proceed to the next experience.
Like professional wine testers who have somehow to obliterate the taste of the previous sip in order to evaluate the next and have developed ingenious ways to do so.
–Rabbi Adin Steinsaltz