might be fine to express a verbal thanks, or regret, but never put it
in your official resignation letter. It just doesn’t belong there.
But the biggest mistake made in the letter of resignation is too
much detail. I have seen resigning employees list the reasons they
are leaving, tell the employer where they accepted the new job, why
they accepted it, their position, responsibilities, salary and bonus
structure. Why would you share this competitive intelligence with a
soon-to-be FORMER employer and possible competitor of your new
employer? This is confidential information - information that can
only be used to emotionally or actually sabotage your new situation.
(Yes, I’ve seen it done, once even calling the new boss and telling
him all the reasons why he just made a bad hire. Really! Fortunately
it didn’t work – the new boss knew a good hire when he saw one.)
Or it can be used as a tool for your old employer to make you a
counteroffer. If your intention is not really to change jobs, but rather
to elicit a counteroffer in order to get a raise from your current boss,
then you have not read the research on why this amounts to career
suicide. We assume you know better.
After you have crafted a resignation letter, you must give it to the
boss. With few exceptions, you should do this in a face-to-face
meeting. Thus it is your responsibility to arrange for a meeting, and
if you arrange the meeting, it is your responsibility to have an
agenda for it. Should the boss want to know what the meeting is
about, simply say it is a matter of “personal concern that needs to
be addressed confidentially.”