DD is an abbreviation for daughter. It stands for "dear daughter".
DH, DS, DD, DW: Dear husband, dear son, dear daughter, dear wife
Oh good, I'm glad you have a trip planned for the 4th. My daughter is gone this time of year too. We don't ever get to spend 4th of July together.
I procrastinate about housework all the time.

But, I do it even more, if I don't think there's any reason to keep things clean, like nobody home but me.
Try to keep busy though, so you don't get down in the dumps.