A little thing called motivation

Why is it that I lose my motivation just when I need it the most?
I did accomplish a lot on Saturday,
Eye appointment and new glasses ordered
New driver's license, it only took an hour and a half for the state to now recognize me as Mrs. C. I did have knitting with me, but I chose to people watch instead. I mean, everyone has to go to the DMV so there is always an interesting variety of people.
Returns and exchanges to three different stores.
Air filters were purchased.
However, as soon as I got home my motivation was sapped and I didn't want to get off of the couch. Later after Little Man went to bed, I did manage to finish up the thank you notes for Elijah's birthday gifts.
Then on Sunday I had grand plans to make these wonderful sounding cinnamon roll type things, but then I discovered my recipe was for a bread machine and I didn't know quite how to convert everything and I gave up. After that I had no motivation to do much of the million things that I wanted and or needed to do.
Does anyone else have times like that?