My trick is to wake up early and accomplish a few things right away. If you lounge about, like you'll be inclined to do, you'll be depressed by noon.
And, I am discovering, so will any kids at your house. They'll hover around you all day (this is seriously annoying), looking for you to help them feel better. They don't know why they're dissatisfied and listless. You'll be in no mood to entertain, but you're the grown up. Deal with it.
If you do get in the dumps, get out of the house. Everyone will feel better (probably even the person you visit). Make a plan for what you'll accomplish when you get home so you avoid walking back through the front door into the same rut.
No, blogging was not part of my plan.