to be forgotten―pass out of mind―pass out of one's memory―fade from one's memory―escape one's memory―slip one's memory―fall into oblivion―be buried in oblivion
忘れやすい傾向
忘れっぽくなる.
忘れる.
to carelessly forget to say something
消し忘れ
the degree to which something is difficult to forget
ゆめ忘るな
to forget something altogether
思い出さずに
Be ever present to your mind
お忘れなく
to forget oneself―lose oneself (in admiration)―be lost (in admiration)―be absorbed (in study)―be engrossed (in one's business)―be beside oneself (with joy or grief)