I may not know you but I see what you mean about representing your personality. It does come across very genuine and personal, even a bit casual and humorous, and I can see your aim is to explain yourself, but without acting differently than you otherwise would, and without making a big emotional production out of it. I respect that and I don't think I can suggest much more for it, especially not without knowing about your life.
I'll second GoodLuck by saying it's best to mention it isn't their fault (assuming they don't have a part in driving you to this point). And if there's anything you've kept from anyone in your life, that you feel like they need to know, or any other wishes or gestures of affection you feel are necessary, add those in. These are what you plan to be your last words, they look appropriate to me, but I think the best advice that can be given here is to consider it done when you personally feel you've said what you need to say. Look it over and edit it until you feel like it doesn't misrepresent your situation, your feelings, or leave out something important.