Reflecting on cfoley & dtj & &Tom_Hagen & fooddude's advice, I've realized that if I find something I can do, know how to do it, and it promises a fun or somewhat valuable outcome, I tend to do it regardless of my fatigue. However, I usually don't assess whether its value aligns with my core values (I actually value my health greatly) or consider other more important tasks I should be doing. This often leads me to push through these initially appealing but ultimately lower-value things, which ironically makes it harder to tackle complex, important tasks, leading to distraction.
The key, as you suggested, is to postpone those low-value materials, move them to a "someday/maybe" list—and prioritize rest. Even a 15-minute nap can make a huge difference in regaining focus for challenging work.
For instance, I woke up at 4 AM today excited to research an AI model setup, something low-priority for my main goals. Instead of just doing it despite being tired, I put it on my "someday/maybe" list and went back to sleep. It felt great to protect my rest, and I'm really thankful for your advices.