Crash Landing

Today started off great and very productive! I got up around 9:00. Hubby and I ate breakfast before he had to go to work. At 11:00 I called the Honda dealership to see if I could bring my car in today for an oil change. I was in luck, they had slots open at noon and 12:30. I took the 12:30. At 11:30 I went to the post office to mail a package for a customer. Then, I went and got the oil change, I cleaned out a bunch of papers and receipts that were in my car--I need them for taxes so I put them with the tax stuff. They washed my car, too--I love that! Now it's not all yucky from the salt used on the street. Finally, I went to the bank and came home. I got home just in time for Hubby to come home on his lunch break. This was about 2:00. Hubby went back to work a little before 3:00. At this point, I sat down on the couch and that was when I was suddenly consumed by exhaustion.
Now it's almost 5:30. Fortunately, I don't have anything else pressing that needs done today. Rounding up my inventory for taxes will just have to wait til tomorrow. I'm not that worried about it. Our tax appointment isn't until the end of the month. I do have time. I just like to have things done in advance so I'm not going crazy at the last minute.
This sudden exhaustion is driving me nuts. I don't understand it. The most physically demanding things I did today was vacuum and make a fire. And that's not demanding at all! I guess I just needed a nap.