will never forget
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)
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
お忘れなく
to forget something
You must not forget.
I never forget it for a moment.
the degree to which something is difficult to forget
忘れる.