Sometimes when I get run down (too much work, exercise, etc) I just mentally and physically shut down. I will have a day much like you describe. What works for me is to just take me time, a full day or evening. I tell DH nicely to go away watch whatever I want on TV and veg.
Amanda
2011 Specialized Epic Comp 29er | Specialized Phenom | "Marie Laveau"
2007 Cannondale Synapse Carbon Road | Selle Italia Lady Gel Flow | "Miranda"
You don't have to be great to get started, but you do have to get started to be great. -Lee J. Colan