This section of the book is from the "Household Companion: The Home Book Of Etiquette" book.
Lady writers have been accused, and perhaps with some reason, of often reserving the most important part of a letter for the postscript. It is an accusation which they should avoid giving cause for. Postscripts are, for the most part, needless, and in bad taste. It is best to pause a few moments before concluding a letter, and reflect whether we have anything more to say. Above all things, none should defer civilities or kind inquiries to this justly-despised part of a letter. To do so is a proof of thoughtlessness or disrespect. " My kindest regards to my cousin Lucy," added as a postscript, looks like what it really is
an after-thought; and is, therefore, not only without value, but, to persons of fine feelings, offensive.
To all writers something will occasionally occur, after finishing the letter, which it is important to state. If to have forgotten it implies no disrespect it may properly be added as a postscript. But if it should indicate a forgetfulness which may possibly offend the recipient, the whole letter had better be rewritten, and the after-thought put in its proper place.