but I have the impression it impacts my productivity and my mood: I get tired, I have low energy, even lethargic.
You are making something come true in your head when it might not be true at all. I used to think I needed breakfast soon as I woke up. Then I went a few days without breakfast till a bit later. It was fine.
What you start to believe adjusts the ceiling and floor of what you can do. Right now you've just moved that ceiling way down.