Dear Miss M:
Apparently, you are under the misconception that I, in searching for and finding another job, have been in some way "out to get you." I'm sorry.
I'm sorry that I stayed your employee for long enough that you've "never had to deal with this before" and therefore you "aren't handling it well."
I'm sorry if I felt that after almost six years of feudal service at your feet I felt like I deserved more than three weeks of what you all term "flex" time, which is really just a cheap ass way of deducting from vacation time anytime any of the staff is sick.
I'm sorry that I ate the crap you give me every day, the inane assignments like, "I know no one else can find this medical provider Dr. Smith, who may or may not still practice in this state and has the most common name outside of the middle east, but can you just 'work your magic'?"
I'm sorry that I got crappy Christmas presents from you that either made me break out or stunk so bad it was obvious you bought them at Big Lots on the cheap and they'd been around long enough to "turn." I'm sorry I spent more in both time and money on Christmas presents for you than you ever did for me. I'm really sorry about that one.
I'm sorry that no amount of notice is time enough to you, because you'd rather be in denial about me leaving and carry on with your waltzing into the office at ten, taking a two hour lunch, and leaving at five on the dot.
I'm sorry that you can't bother to exchange pleasantries with me anymore, or really look me in the eye since Friday. I'm sorry that you act like one of those popular girls in high school that has finally squeezed all the help she's going to get out of the poor geeky awkward smart girl and who now will have nothing to do with.
Mostly I'm sorry I've wasted so much time and energy worrying about what you think or feel or want when it is immaterial to the situation: I've given my notice. I'm leaving. Be a grown-up-type boss and deal with it.