Seems like many of us are suffering with fatigue right now. Must be the change of seasons.
I don't work outside the home any longer so it's easier for me to take breaks whenever I feel the need.
I just do what I feel I can and if I need to stop and rest I do. I just don't push myself to do more than I'm comfortable with anymore. It's just not worth it.
Maybe a nap in the afternoon would help....if you can manage it. I've found I just have to remain flexible 'cos just as soon as I think I have something figured out it changes on me!