You have been racing with yourself to get things done as planned. So you have been overdoing things too much and the body needed to recuperate.
I have been very busy with errands outside and I had to drive almost everyday. After three days of non stop activities, I sat still and didn’t travel on the fourth day. I just gave myself a holiday and became lazy. So, the following day, I would have the energy to do more work.
How the body and mind swing from inertia to energetic phase!